St. Petersburg, Dec 28 (IANS): At least 10 people were injured in a blast inside a shop in Russia's second largest city, St. Petersburg, the media reported.

According to emergency services sources, an unidentified device exploded in a shop, which prompted the evacuation of at least 50 people, Sputnik news agency reported.

Preliminary data shows that an explosive device found at the scene contained 200 grams of TNT, CNN reported citing RIA news agency.

The device was inside a locker at a chain supermarket called Perekrestok, located in an entertainment complex.

The Russian Investigative Committee's spokeswoman Svetlana Petrenko told Sputnik that investigators would verify all possible causes of the explosion.

Police, bomb-disposal experts and rescuers have arrived at the scene. There has been no fire as a result of the explosion, and the building has not been damaged much, informed sources said.

"At the moment the store is closed, buyers and staff have been evacuated. Special services are working at the scene. There is no more detailed information at the moment," the press service of the retail chain said.

The Russian Investigative Committee launched a criminal investigation after the explosion, while its head, Alexander Bastrykin, has departed for St. Petersburg in order to examine the circumstances of the blast.

Nine persons have been taken to hospitals, the city's deputy governor's office spokesperson said.