A police spokesperson confirmed that "a package at the location caught alight" and it was "dealt with by staff and the local fire brigade at the time".

They added: "Due to the circumstances, and the specialist capability and expertise in investigating such matters, the investigation is being led by officers from the Met's Counter Terrorism Command with support from colleagues from Counter Terrorism Policing West Midlands.

"As part of our enquiries, officers are liaising with other European law enforcement partners to identify whether this may or may not be connected to any other similar-type incidents across Europe."

No one was injured and the blaze was extinguished by the local fire brigade during the incident in Minworth, Birmingham, on 22 July, officers said.

Sky News understands that part of the police's investigation is whether Russia had any involvement in the incident.

No arrests have been made.

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It comes as authorities in Germany investigate several fires thought to have been caused by incendiary devices hidden inside parcels at a warehouse in Leipzig earlier this year.

Officials warned businesses in August that "dangerous parcels" might be in circulation.

On Monday, Thomas Haldenwang, the head of Germany's domestic intelligence agency, told a parliamentary committee that a plane crash had only narrowly been averted when an air freight parcel caught fire.

The prosecutor general's office in the country declined to comment on a possible link to Russia.

A spokesperson for DHL 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."