A fourth man was arrested by police Monday over a series of arson attacks targeting properties linked to British Prime Minister Keir Starmer, London’s Metropolitan Police said.

The 48-year-old was detained at Stansted Airport northeast of London on suspicion of conspiracy to commit arson with intent to endanger life.

The Met’s Counter Terrorism Command is leading the investigation into the three separate incidents in London – a car fire and two separate blazes at homes last month – all linked to properties associated with the premier.

The three other suspects – two Ukrainians and a Romanian aged between 21 and 43 – have all been charged in connection with the fires.

One was charged with three counts of arson with intent to endanger life. The other two face one count each of conspiracy to commit arson with intent to endanger life.

They will appear at London’s Old Bailey court on Friday.

Police did not disclose the nationality of the fourth man arrested.

On May 12 they had opened an investigation into a fire that caused damage outside Starmer’s former family home in Kentish Town, north London, on the night of May 11.

Starmer still owns the property, UK media reports said, but he moved into the prime minister’s official residence in Downing Street after his Labour party’s election victory last year.

Police said they were also investigating another fire at a property linked to Starmer on May 11 and a car that was set alight on May 8.