A bomb hidden behind a kiosk exploded in a crowded market Friday in central Russia, killing eight people and wounding 37, prosecutors and emergency officials said.

The bomb, which went off about midday in the Kirov market in Samara (search), 500 miles southeast of Moscow, contained about two pounds of plastic explosives (search), regional prosecutor Alexander Yefremov said, according to the ITAR-Tass news agency.

Russian state television showed pictures of bloodied bodies covered with plastic tarps, surrounded by debris. The blast ripped apart corrugated metal kiosks used as market stalls.

"The explosion was very powerful, and the place was packed with people," said Timofei Zakharchenko, a spokesman for the Samara branch of the Emergency Situations Ministry.

He said eight people were confirmed dead and 37 were injured.

The explosive was placed on the back wall of one of the kiosks, ITAR-Tass said. Interfax said that the epicenter of the explosion was near a railway that ran alongside the market.

Prosecutors opened a criminal investigation on charges of terrorism and murder, ITAR-Tass reported, but officials did not say whether they suspected political terrorism or a business dispute was behind the blast.

Earlier, emergency officials in the city said the blast was from two gas canisters that exploded while being used to cook food at an outdoor eatery.

Gas canisters are widely used in Russia at outdoor markets and street food stalls, and explosions are common. Four people were killed in an explosion of canisters in March in the Siberian city of Omsk and a May 2003 blast in Moscow killed one and shattered the outdoor terrace of a restaurant.