It is understood one potential line of enquiry is whether the incident in July 2024 was part of a Russian-backed plot.
Counter-terrorism police investigating a fire at a DHL warehouse in Birmingham have arrested a man on suspicion of assisting a foreign intelligence service.
The Metropolitan Police said a 38-year-old Romanian national was detained at Stansted airport after flying into the UK on 19 March.
Counter Terrorism Policing (CTP) began an investigation after a package caught fire on 22 July at the warehouse in Minworth, near Birmingham.
Police confirmed "a package at the location caught alight" and it was "dealt with by staff and the local fire brigade at the time". No one was injured.
It is understood that one potential line of enquiry is whether the incident was part of a Russian-backed plot.
In November, Polish officials stated they believed the fire could have been a trial run for an attack targeting cargo flights to the US.
Poland's National Prosecutor's Office confirmed they had made four arrests after parcels "containing explosives" were allegedly sent via courier companies to countries including the UK.
At that same time, German authorities were also investigating several fires thought to have been caused by incendiary devices hidden inside parcels at a warehouse in Leipzig in 2024.
On Thursday, police confirmed their "investigation remains ongoing", adding the man they arrested was "detained on suspicion of assisting a foreign intelligence service under the National Security Act".
He was taken to a London police station and released on bail to a date in July.
A spokesperson for DHL previously said: "DHL Express Europe is taking risk mitigation actions to secure its network, staff and assets as well as customer shipments by implementing strengthened security measures across the European countries as a reaction to ongoing investigations by authorities from several countries."
