A fire in a wooden apartment building in a small Russian town has killed six people, four of them preschool-age children.

No cause has been determined for the Saturday night fire in Pesochnoe, about 250 kilometers (150 miles) north of Moscow. News reports cited witnesses as saying it was preceded by an explosion.

The regional branch of Russia's Emergencies Ministry said six bodies were found in the wreckage, four of them children. The Investigative Committee said they included two one-year-old children and two others aged two and three.

The emergencies ministry said twenty people were evacuated from the 99-year-old two-story building, which was destroyed.