An attacker on Sunday threw firebombs at an immigration office used to process asylum seekers crossing the Channel in small boats as the government seeks to curb record arrivals.
Kent Police said that on Sunday morning "two or three incendiary devices" were thrown into a centre processing immigrants in the Channel port town of Dover in southern England, injuring one.
The BBC quoted the Home Office as saying the attack took part at the Western Jet Foil Border Force centre in the major Channel port town, used to process asylum seekers.
Police said that "one minor injury has been reported" and the suspect "has been identified and located", without giving further details.
Kent Live local news website posted photographs of police and fire services at the scene near the Port of Dover, and the BBC reported that a fire was put out.
Immigration Minister Robert Jenrick tweeted that there had been a "serious incident" and "my sympathies are with those involved".
Dover's Conservative MP Natalie Elphicke tweeted: "I am deeply shocked by the incident in Dover today. I have spoken to the immigration minister (Jenrick) about the situation. My thoughts are with everyone involved."
Elphicke later told LBC Radio: "I understand that the Dover immigration centre that is at the Port of Dover was firebombed by a number of devices before an individual committed suicide."
Police have not confirmed reports that the attacker killed themselves.
Elphicke told LBC: "We don't know the motivation of the individual concerned yet."
Read more on FRANCE24
UK's Truss urges French action as Dover delays cause summer holiday chaos
Thousands of virus-stranded trucks depart Dover for Calais
Lorry queues grow in Dover as EU set to meet over UK trade, travel ban