BARCELONA — Spanish police expanded their hunt Friday for a man who swerved his van onto Barcelona’s Las Ramblas promenade, as evidence of a wider web of plotters took shape after the worst terrorist attack on Spain in more than a decade.
Investigators were still untangling the chain of events. But they believe at least eight people plotted Thursday’s Barcelona attack and another one south of the city early Friday, which evinced a level of sophistication comparable to major strikes in Paris and Brussels in recent years. Other more recent attacks in Nice, Berlin and London were perpetrated by individuals operating largely on their own.
In a sign that the attack could have been significantly worse, police said that a major gas explosion destroyed a house being used by the assailants hours before the van veered into crowds in Barcelona. Propane and butane canisters were found on the scene, and authorities believed they were intended for use against civilians.
As of Friday evening, authorities had detained three Moroccan men and a Spaniard, but the main suspect — the driver of the van, who fled on foot after the rampage — was believed to remain at large. Police also were investigating the possibility that he was among five assailants killed in the second attack early Friday.
Meanwhile, the nation began to mourn the international group of at least 13 victims who were fatally struck as they strolled in the heart of Barcelona’s tourist district late Thursday afternoon.
In Washington, the State Department said Friday that an American was among those killed. The department also said Spanish authorities still have not identified all of the casualties, so the U.S. Consulate in Barcelona is working with them to determine whether any more Americans were killed or injured.
Also on the forefront for investigators: trying to piece together the extent of the network that carried out Thursday’s carnage in Barcelona and a second vehicle rampage in Cambrils, a seaside town about 60 miles south of Barcelona, that left at least one person dead — raising the overall death toll to 14.
The Islamic State claimed links to the Barcelona attack, but the level of involvement by the militant faction was unclear.
Spanish intelligence officials were circulating at least four names among their European counterparts on Friday, according to a Spanish intelligence official and a European intelligence official, both of whom spoke on condition of anonymity to discuss the situation.
The four men, all holding Moroccan citizenship, ranged in age from 18 to 24. Three were born in the North African country: Said Aallaa, 18; Younes Abouyaaqoub, 22; and Mohamed Hychami, 24. The fourth was identified in a Spanish police document as Moussa Oukabir, 17, but the European intelligence official said Spanish officials had flagged someone with the same family name but a different first name. All lived in or near the Catalan town of Ripoll, close to the French border.
At least three of the men were killed in the attack in Cambrils, the Spanish intelligence official said, without identifying which of the men were believed killed.
Two Spanish security officials said police originally sought Oukabir’s older brother because his identity card was found in the truck used for the attack in Barcelona. The older brother, who is currently in custody, denies any connection to the attack and said his brother may have stolen his identity card, the official said.
“We cannot rule out further attacks,” Maj. Josep Lluis Trapero, a Catalan police official, told reporters in Barcelona.
Trapero said police were still trying to determine whether the driver of the van in Barcelona was killed in the second attack.
The nationality of the men was sure to raise alarm within European counterterrorism circles. Moroccan networks were also connected to major terrorist attacks in France and Belgium in recent years. Spain has a significant Moroccan population, and there has been a spike in arrivals of migrants from Morocco by sea this year.
Authorities were not aware of any previous connection to extremism among the detained men, Trapero told reporters in Barcelona.
In Cambrils, police said all five men who plowed their Audi into people along the corniche at about 1 a.m. were shot dead, four of them by the same officer.
In Barcelona, thousands of people gathered in a square at the top of Las Ramblas for a minute of silence, led by Spanish King Felipe VI and Prime Minister Mariano Rajoy. Afterward, they cheered, held single red roses to the sky and chanted in Catalan: “I am not afraid.”
In a sign of the evolving investigation, Rajoy led an emergency meeting of security officials in Barcelona. The meeting included a review of all leads in the manhunt for the driver and an analysis of “the latest details” on the attacks in Barcelona and Cambrils.
The whole Las Ramblas neighborhood was eerily quiet as heavily armed police patrolled on Friday.
Tourists and onlookers slowly filled the long boulevard, turning what is ordinarily a vacation hotspot into a site of mourning. Some set out candles to commemorate the victims.
In a series of tweets, President Trump said U.S. agencies were “on alert” and blamed court challenges and opposition from Democrats for making security “very difficult.” He gave no specifics.
“Radical Islamic Terrorism must be stopped by whatever means necessary!” Trump wrote. “The courts must give us back our protective rights. Have to be tough!”
The attacks on Thursday and Friday marked the latest uses of vehicles in terrorist strikes against civilians.
Spain’s civil protection agency said 120 people were injured in the attack in Barcelona, and an additional six in Cambrils. There were casualties among people of at least 34 nationalities, underscoring the international draw of the cosmopolitan Las Ramblas area, which has long stood at the heart of the city. France’s Foreign Ministry said 26 of its citizens were injured, 11 of them seriously.
Residents of Barcelona said they had long feared an attack on their bustling city.
“This is a huge city, and somehow we were always expecting something like this, but of course you’re never prepared,” said Cristina Nadal, 44, an aide for the Catalan government, who came to the moment of silence on Friday.
The crowd was “exactly what we wanted to show — that although the terrorists want to beat us, we can show to the world that we can still stand strong,” she said.
Two longtime Muslim residents of Barcelona said they were furious about the violence.
“What Islam teaches us is that killing one person is like killing all of humanity,” said Nagma Jawed, 40, who moved to the city 20 years ago from her native India and runs a textile shop in the city.
“First of all, we are human beings. Our religion comes after that,” said Jawed, who was wearing a headscarf on Friday as she stood in the square with her husband for the mourning ceremony.
It was not immediately clear how closely the Islamic State had worked with the attackers. The group has previously claimed responsibility for attacks inspired by its rhetoric but not directly planned by Islamic State leaders.
Police later said they were looking into a potential link between the van attack and a pair of earlier explosions that destroyed a house in Alcanar, about 100 miles southeast of Barcelona. One person was killed there and 16 were injured, including police officers and firefighters who were investigating the initial blast. The blast at the housewas initially reported to be a gas explosion.
At least one of the three men in detention was involved in the explosion, one of the Spanish security officials said, and counterterrorism authorities were proceeding on the assumption that the propane canisters were intended for use as part of an attack and exploded prematurely.
Birnbaum reported from Brussels and Mekhennet reported from Frankfurt. William Booth and Raúl Gallego Abellan in Barcelona, Paul Schemm in Addis Ababa, Ethiopia and Brian Murphy in Washington contributed to this report.