GENEVA (Reuters) - Two Syrian men were arrested in Geneva on Friday after traces of explosives were found in their car, Switzerland’s attorney general said on Saturday, confirming media reports.

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Criminal proceedings have been opened against the two under a law prohibiting groups such as al Qaeda and Islamic State, a statement from the attorney general’s office said. It did not give any names or other details about the pair.

They denied criminal intent but are to be handed over to Swiss federal police, Geneva prosecutor Olivier Jornot told a news conference.

The two men, who had two valid Syrian passports, had been stopped by Geneva gendarmes, he said. “Due to their behavior and their nationality they were subjected to extra checks.”

They did not speak French and said they had only just arrived in Geneva and recently acquired the car. It was possible that the traces of explosives in the car had no link to them, he said.

The attorney general’s initial statement said the men were suspected of making, hiding and transporting explosives or toxic gas. Jornot clarified however that the relevant law covered both explosives and toxic gas, but there was no suspicion of gas in this case.

Police in the Swiss city, home to the European headquarters of the United Nations, the Red Cross, and many banks and trading houses, moved onto a high state of alert earlier this week after a suspicious Belgian-registered vehicle fled from a late-night police check and crossed the border into France.

Geneva’s Le Temps newspaper reported on Thursday that one of the two occupants was a friend of Salah Abdeslam, the man wanted in connection with the Paris attacks on Nov. 13.

On Friday Swiss President Simonetta Sommaruga said federal authorities had been tipped off by foreign authorities about a suspected Islamic State cell in the region.

Two sources confirmed to Reuters the U.S. Central Intelligence Agency had provided a photo of four men to Swiss authorities on Wednesday, saying they could be on Swiss territory.

The photo, published in Swiss newspapers, showed four bearded men seated, with their faces blurred and index fingers raised in the air.

But Jornot said there was no indication the men were on Swiss territory, and no connection between the various strands of investigations had been established.

He said the heightened security alert in Geneva had prompted many calls from the public and led to the arrest of another man with an “absolutely impressive arsenal” including a Kalashnikov machinegun, Glock pistols and about 30 antique muskets. The man also had Nazi flags and was not linked to the other investigations, Jornot said.

“There will definitely be more arrests in the next few days because the police have an enormous amount of information. But it doesn’t mean that each time we put our hand on someone that we have found a terrorist. We are just doing our job,” he said.