TOWN OF LITTLE FALLS, Wis. (AP) — Four children died with their pets in a house fire in a small town in east central Wisconsin, authorities said.

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

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Captain Jeffrey Spencer of the Monroe County Sheriff’s Office said the four victims were children. The sheriff’s office and fire department have not released the names or ages of the victims.

The home was fully engulfed in flames by the time firefighters and sheriff’s deputies arrived, officials said. Firefighters tried to get inside to rescue them, but were driven back by the intense heat, smoke and fire, Arnold said. Firefighters extinguished the blaze from outside.

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Arnold said one person who escaped to a neighboring property to call 911 had tried without success to alert others to the fire.

Arnold said the search for victims was hampered by the collapse of the second floor during the fire. He said the victims, along with several dead pets, were found on the first floor.

The cause of the fire hasn’t been determined and Arnold said more information would be released after an investigation.

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Little Falls, with a population of about 1,300 people, is about 140 miles (225 kilometers) northwest of Milwaukee.