MOSCOW — Russian news reports say at least four people have been injured by an explosion at a supermarket in St. Petersburg.

Russian news agencies quoted St. Petersburg’s branch of the Emergencies Ministry as saying that a device containing 200 grams (about 7 ounces) of explosives went off on Wednesday at a storage area for customers’ bags.

No one has claimed responsibility for the explosion at the market in the city’s northwest Kalininsky district.

The Investigative Committee has sent experts to look into the explosion.

Russian President Vladimir Putin telephoned US President Donald Trump earlier this month to thank him for a CIA tip that helped thwart a series of bombings in St. Petersburg.

In April, a suicide bombing at a Russian subway station left 16 people dead and wounded more than 50.