An initial investigation suggested a gas leak was to blame, but other possible causes including terrorism were also being considered, said Marat Prokopenkov of the Emergency Situations Ministry's branch in southern Russia.

Attacks on law-enforcement officials are common in Ingushetia, which borders war-scarred Chechnya. Near-daily outbreaks of violence stem from Islamic militancy, business and personal rivalries and deep-seated anger at government oppression and heavy-handed police tactics.

Rescue workers recovered six bodies from the rubble of the three-story brick building, which served as the headquarters of the regional bailiffs' service in Ingushetia's main city, Nazran, Prokopenkov said. Another 23 people were pulled from the debris alive, but one of them - a woman who worked for the bailiffs' service - died in the hospital, he said.

One of the injured was in critical condition, Prokopenkov said.

Rescuers picked through the debris for more possible victims. Authorities cordoned off the wreckage site, where the building's facade was blown away and its top story hung precariously over the gutted interior.

A spokeswoman for the regional branch of Russia's top investigative body, Svetlana Gorbakova, said the dead included four women and three men.

She also said authorities suspected a gas blast. Deadly explosions of gas used for cooking and heating are common throughout Russia, which is plagued by shoddy construction and safety violations.

In the capital of Dagestan, another North Caucasus province, a bomb exploded beneath a police officer's car Tuesday after he got behind the wheel, severing his legs and leaving him in serious condition in hospital, police spokesman Shamil Guseinov said.