British counterterrorism police have re-arrested two men on suspicion of assisting Iranian intelligence in an investigation into a suspected plot near RAF Fairford, the British airbase used by American bombers to strike Iran. Investigators say Iranian state involvement is highly likely.

The suspects are a 24-year-old British national and a 25-year-old British-Iranian dual national, both from Westminster in central London. They were detained under the National Security Act after previously being released on bail. The younger man was originally arrested near Fairford; the older suspect was arrested later in London.

“We consider it highly likely that there is Iranian state involvement,” said Assistant Commissioner Laurence Taylor, head of Britain’s Counter Terrorism Policing. He said investigators were still examining the extent of that involvement and what the operation was intended to achieve.

Seven men have been arrested during the investigation. The other five remain on bail, and no one has yet been charged.

The case began last month after reports of three suspicious vehicles traveling toward Fairford brought armed officers to nearby Whelford in Gloucestershire. Five men were arrested, a security cordon was established and around 85 households were evacuated as a precaution while Army bomb-disposal specialists examined the vehicles.

Police subsequently confirmed that gasoline had been recovered, but no improvised explosive devices were found. The initial arrests were on suspicion of explosives offenses and preparing a terrorist act. Authorities stressed that releasing the men on strict bail conditions did not end the investigation.

American B-1 bombers were withdrawn from Fairford after the incident. British Prime Minister Andy Burnham has said the activity near the base was likely coordinated in Iran. Iran’s ambassador to Britain has denied Tehran’s involvement.

The re-arrests follow a wider warning from MI5 Director General Ken McCallum, who said Iran-linked operations had led to more than 50 arrests in Britain over the previous year. In his latest threat assessment, he described Tehran’s continued use of criminal proxies against Iranian opposition figures, media organizations and Israeli sites, with much of its aggression aimed at British Jewish communities.

McCallum also attributed a wave of arson and sabotage attacks against Jewish targets in Britain and elsewhere in Europe to a front group backed by members of Iran’s Islamic Revolutionary Guard Corps. Those targets included synagogues, ambulances and businesses. Alongside those threats, he warned that Iran was increasingly seeking to strike harder targets, including military installations.