President Donald Trump said Thursday that Iran appeared to have been involved in the RAF Fairford incident, but stopped short of confirming a connection to the British base used by US bombers for strikes on Iran. “Looking like they were. I can't say that with confirmation, but it's looking like that,” he told reporters after landing in Texas.

British counterterrorism police arrested a sixth suspect Thursday, a 25-year-old dual British-Iranian national, in Westminster on suspicion of preparing terrorist acts. Five British men arrested near the Gloucestershire base on Sept. 27 remain under investigation on bail with strict restrictions. Police recovered petrol from three vehicles but found no improvised explosive devices, and are examining possible foreign state involvement.

Prime Minister Andy Burnham said Wednesday there were “strong indications” Iran played a part, while stressing that the investigation remained ongoing. Israeli Prime Minister Benjamin Netanyahu separately told Fox News that Israel had warned Britain of an Iranian-sponsored attack and complained that London imposed sanctions on Israel shortly afterward. Iran denies involvement and summoned British Ambassador Hugo Shorter on Thursday to protest allegations its Foreign Ministry called “baseless.”