British police on Tuesday arrested a 22-year-old man in London on suspicion of a terror offence over a security incident at a U.S.-run military air base in England that authorities have linked to Iran.

The arrest is the seventh in connection with a suspected plot against RAF Fairford, located 100 miles (160 kilometers) west of London, which has been used by American bombers to strike Iran during this year’s war.

Counter Terrorism Policing said the man, a British national, was detained in the Westminster area of central London on suspicion of preparation of terrorist acts.

Six other men have been released on bail under investigation.

Vicki Evans, the senior national coordinator for counterterrorism policing said detectives “continue to pursue multiple lines of enquiry” and “remain committed to investigating all possible angles.”

Scores of residents were evacuated from their homes near the base early on Sept. 27 as armed police officers and army bomb-disposal experts swooped on the rural area. Police later said they had found a quantity of an accelerant — gasoline — in three vans linked to the five suspects, but no explosives.

Prime Minister Andy Burnham has said the U.K. sees “strong indications” that Iran played a part in the incident, without saying why or what the nature of the suspected plot was.

Iran has denied involvement, but it has previously said it considers any base used to attack its territory a legitimate target.

The U.S. moved its B-52 and B-1 bombers from RAF Fairford on Sunday, though it’s unclear whether the move is connected to the arrests. U.S. President Donald Trump told reporters on Monday that he didn’t want to tempt “the enemy” by having the bombers there.

“We had a threat, and if we’re going to be threatened, we would just move them, and that sort of alleviates that,” he said in Washington. He said that the people who made the threat “would be linked to Iran,” but he didn’t offer details.