ST. CHARLES, Ill. (AP) — A weekend fire that damaged portions of a shuttered suburban Chicago resort took firefighters a full day to extinguish and officials are still working to determine how it started.

The fire began Saturday afternoon at the former Pheasant Run Resort in St. Charles, sending huge plumes of smoke into the sky. More than 20 local fire departments, including the St. Charles Fire Department, battled the blaze before it was extinguished late Sunday afternoon.

No firefighters or civilians were injured in the fire in St. Charles, a city in DuPage and Kane counties that’s about 35 miles (56.3 kilometers) west of downtown Chicago.

The blaze was contained to the center structures of the shuttered 18-acre complex, Deputy Chief Erik Mahan with the St. Charles Police Department told the (Arlington Heights) Daily Herald.

He said investigators are still trying to determine how the fire began, saying that “many questions are unanswered.”

While the idled resort had been the target of vandals during the past year, Mahan said there is no evidence anyone had been living on the closed property before the fire began Saturday.

The Pheasant Run Resort closed in March 2020 after attempts to auction the property were unsuccessful.