LONDON — A 22-year-old British man arrested on suspicion of plotting a terror attack following a security incident at a U.S.-run military air base in England has been released on bail, authorities said Thursday.

The suspect, who was not named, is the seventh man bailed in the investigation of an apparent plot aimed at RAF Fairford air base, which has been used by American bombers to strike Iran.

British authorities have linked Tehran to the incident that led the U.S. to pull its bombers from RAF Fairford on Sunday.

The Trump administration believed the base faced Iranian threats intended to kill as many American troops and destroy as many U.S. planes as possible, according to a U.S. official, who was not authorized to comment publicly on the matter and spoke on condition of anonymity.

Prime Minister Andy Burnham has said the U.K. sees “strong indications” that Iran played a part in the incident. He did not provide details about what the suspects were planning or why the U.K. thinks Iran was involved.

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

Police are continuing to investigate the incident that led to scores of residents being evacuated from their homes near the base on Sept. 27 as armed police officers and army bomb-disposal experts swarmed the rural area.

Police later said they had found a quantity of an accelerant — gasoline — in three vans linked to the initial five suspects, but no explosives.

All the suspects arrested have been in their 20s and six have been British nationals while one is a dual U.K.-Iranian citizen.

The U.K.-owned base, 100 miles (160 kilometers) west of London, was used by American B-1 and B-52 bombers during the Iran war.

The British government allowed the U.S. military to use RAF Fairford for what it called defensive strikes on Iranian missiles and their launch sites following Iranian attacks on U.K. interests and Britain’s allies in the Gulf.