The United Kingdom raised its terrorism threat level to critical, the highest level possible, Saturday after a vehicle plowed into the terminal building at Scotland's busiest airport and burst into flames.
Police at the highest levels are assuming the fiery incident in Glasgow was a terrorist attack, CNN has learned.
Authorities assume the incident is linked to the discovery Friday in London of two explosives-filled cars. They could not yet say whether the same people were involved or whether the Glasgow incident was the work of copycats.
Police and witnesses in Glasgow described an SUV-style vehicle in flames being driven at full speed toward the building.
Two people were arrested at the scene, police said.
It was not immediately clear whether there were any injuries, although unconfirmed witness reports described a man on fire at the scene.
Witness Jackie Kennedy said a man got out of the car, went to the back and pulled out a can of fuel, which he poured on himself and ignited.
"The guy was in flames and seemed to be enjoying himself," Kennedy said.