An apartment building explosion in Russia's northern city of Arkhangelsk early Tuesday killed at least 32 people, leaving several others trapped in debris, crisis center in the city said. 

Twenty-four residents in the building have been saved, but the death toll might continue to rise as 12 others are feared to remain trapped in the rubble and seven of the 14 hospitalized are in critical situation, Itar-Tass News Agency reported.

Terrorist attack has been earlier suspected of causing the blast, but investigators believe that the most likely reason behind the tragedy could be a natural gas explosion "through somebody's negligence or premeditation," Interfax news agency quoted sources from the crisis center as saying. 

Police were searching for two men suspected of involvement in the explosion. Eyewitnesses say they saw them carrying metal pipes and tools out of the house shortly before the explosion.

Two middle-aged men might have stolen the gas valves, which caused a leakage of household gas and the subsequent explosion. City police said gas valves have been missing in two nearby houses where gas leakage was registered.

The blast erupted at 3:00 am Moscow time (0000 GMT) when 63 residents registered in the apartment building in Arkhangelsk, 960 kilometers north of Moscow, where sleeping.

A fire broke out after the building collapsed, hampering rescue work. The debris of the 6th, 7th, 8th and 9th floors have been cleared, and rescuers are working on the fifth floor.

More than 800 rescuers will continue working throughout the night. The temperature in Arkhangelsk is minus 2 degrees Celsius, under which people can survive for about two days, the rescuers say.

Arkhangelsk prosecutors opened a criminal investigation into the accident on charges of death and damage by negligence.

Neglect of safety precautions has led to frequent gas explosions in Russian apartment buildings and public facilities.

Moscow police are checking attics, basements and other housing facilities in case of gas system malfunctions.

(Xinhua News Agency March 17, 2004)