Nineteen people are confirmed dead from the New Year’s Eve collapse of an apartment building in the Urals city of Magnitogorsk, as rescuers continue to pull bodies from the rubble in frigid conditions and speculation about the cause of the disaster swirls.

The Russian Emergency Situations Ministry said on January 2 that about 25 people remained unaccounted for after an explosion caused part of the building to collapse, leaving dozens of people homeless over the holiday.

Two children were among those confirmed dead, the ministry said. Six people, including two children, were rescued from the rubble and hospitalized.

Russian authorities have said since shortly after the December 31 collapse that a natural-gas explosion was the most likely cause.

But in a statement issued on January 1, the federal Investigative Committee said the authorities were looking into “all possible causes” and added that no signs of a bomb blast have been found.

“In connection with various reports that have appeared in the media, it must be noted that at the present moment…no traces of explosives or their components have been found,” the statement said.

The committee issued the statement after two media outlets cited unnamed sources as saying that possible traces of explosives were found at the site and that the blast that caused the collapse could have been a terrorist act.

The reports in and regional news site, which could not be independently verified, also linked the building collapse with an incident late on January 1 in which a van caught fire some 3 kilometers from the site, killing three people.

The site cited unnamed law enforcement sources as saying that the occupants of the vehicle were suspects who were being sought by police, possibly in connection with the building blast and collapse.

The Federal Security Service (FSB) said that there were two gas canisters in the vehicle, and the regional Interior Ministry branch said that the fire may have been caused by a gas-canister explosion.

Speculation was stoked by Internet-posted footage of the burning van in which a series of loud bangs that sound like gunfire can be heard.