A Border Force migrant centre in Dover was petrol bombed by a man who then killed himself on Sunday.
Eye witnesses said the man drove a white Seat vehicle up to the Tug Haven processing facility in Kent, before throwing three incendiary devices, causing a fire.
The witness said fireworks were attached to the molotov cocktail-style devices, one of which did not detonate.
Police arrived within minutes of the attack and cordoned off the area at the Viaduct in Dover at 11.22am on Sunday.
A suspect was later identified and located at a nearby petrol station, where he was confirmed to have died, police said.
Following the incident, Kent Police said: "Officers established that two to three incendiary devices had been thrown outside and into the premises by a single suspect who arrived at the scene in a car. Two people have reported minor injuries from inside the property.
"The suspect was identified and very quickly located at a nearby petrol station, and confirmed deceased."
It added that the Explosive Ordnance Disposal Unit attended the scene and located another device, which was "confirmed safe within the suspect’s vehicle".
Official sources on Sunday indicated that the incident was not thought to be terror related. Local sources said the man had a history of mental health problems.
The incident came after almost 1,000 migrants arrived in the UK after crossing the Channel on Saturday. Many were still in the centre when it was attacked.
Police confirmed that the processing facility remained open throughout the day, but that "around 700 suspected migrants were relocated" to the main asylum processing centre at Manston airfield nearby in Kent.
Suella Braverman, the Home Secretary, tweeted on Sunday: "There was a distressing incident in Dover earlier today. I am receiving regular updates on the situation.
"My thoughts are with those affected, the tireless Home Office staff and police responding. We must now support those officers as they carry out their investigation."
Robert Jenrick, the immigration minister, who visited the scene, added: "Earlier today there was a serious incident at Dover. I am being kept regularly updated by the police.
"My sympathies are with those involved and my thanks and admiration are with Kent Police and Border Force officers as they go about their essential work to keep us safe."
Natalie Elphicke, the Conservative MP for Dover, said she was "deeply shocked" by the attack. "I understand that the Dover immigration centre that is at the Port of Dover was firebombed with a number of devices, before an individual then committed suicide," she told LBC radio.
She added that whilst the motivation of the perpetrator is so far unknown, the centre is "a well-known facility" where small boats arrive.
"It's an absolutely dreadful situation that we have now at Dover," she said. "I understand that all the people who are at the centre are being looked after and precautions are being made for their safety."
She added: "I think it is fair to say that tensions have been running high over the last period. And indeed, I'd raised my concerns about that with the immigration minister earlier this week."
