TOWN OF LITTLE FALLS, Wis. (AP) — Four people have died in a house fire in small town in east central Wisconsin, according to authorities.

Sparta Area Fire District Chief Mike Arnold said crews responded shortly after 9 p.m. to a report of a house fire with people trapped upstairs in the Town of Little Falls.

By the time firefighters and Monroe County sheriff’s deputies arrived the home was fully engulfed in flames, officials said.

Firefighters tried to get inside to rescue the people trapped, but were driven back because the heat, smoke and fire were too intense, Arnold said. Firefighters extinguished the blaze from the exterior.

Arnold said another person inside was in a different part of the house, tried to alert others to the fire before going to a neighbor to call 911.

The second floor collapsed during the fire, which Arnold said hampered the search for victims. He said the four victims, along with several dead pets, were found on the first floor.

The fire department hasn’t released the names of the victims. The cause of the fire hasn’t been determined, and Arnold said more information will be released after the investigation.

Firefighters from Black River Falls and Melrose, along with first responders from Black River Falls, Sparta and Cataract, assisted at the scene.

The town, with a population of about 1,300, is 40 miles (64.3 kilometers) northeast of La Crosse.