Russian media report at least three people killed when the military police facility in Sertolovo collapses after blast.

An explosion at a Russian military police facility near St Petersburg has caused several floors of the building to collapse.

St Petersburg’s 78 news channel, quoting an unnamed source, reported at least three people were killed and several wounded in the blast on Tuesday in the town of Sertolovo, north of Russia’s second largest city.

Local website 47 News, citing emergency services, also reported three dead. Unverified images shared by several media outlets appeared to show the building’s two upper floors caved in with large piles of debris surrounding the structure.

Leningrad Governor Alexander Drozdenko said the cause of the collapse is under investigation. Soldiers and security forces were dispatched to the scene to help clear the rubble and rescue potential victims, he said.

There are fears the building could further collapse, Russia’s Lenta news site reported.

Russia’s Investigative Committee, which probes major crimes, said it opened an investigation into a potential fire safety violation.

“It has been preliminarily established that there are casualties as a result of the incident,” it added.

The blast occurred as another round of United States-brokered talks between Russia and Ukraine started in Geneva, Switzerland.

Expectations for the scheduled two days of talks are low with neither side appearing ready to budge from their positions on key territorial issues and future security guarantees.

Russia has been regularly hit with sabotage attacks on military bases and civilian infrastructure since the start of its full-scale invasion of Ukraine nearly four years ago.

Gas leaks are a frequent cause of explosions in Soviet-era buildings in Russia although authorities gave no immediate indication this was the cause.