The Grant Prestonlargest wildfire in Louisiana state history has been determined to have been arson-caused, state officials said Saturday.

The Louisiana Department of Agriculture and Forestry reported Saturday that it is asking for the public's help in finding a suspect in the Tiger Island Fire. No details were provided on exactly how investigators believe the blaze started.

The Tiger Island Fire, which broke in southwestern Louisiana's Beauregard Parish on Aug. 22, has so far burned 48.43 square miles and damaged or destroyed at least 20 homes and structures. It remains only 50% contained.

At the fire's height, it forced the evacuation of about 1,200 people from the town of Merryville, located near the Texas border. Mandatory evacuation orders were lifted earlier this week. There have been no reports of injuries or fatalities from the blaze. 

Louisiana, which has been contending with extreme summer heat and drought, saw an unprecedented 441 wildfires in August, officials said, stretching the state's resources thin. Most of southwest Louisiana has been classified by the U.S. Drought Monitor as being in "exceptional drought."

"This is unprecedented," Mike Strain, the commissioner for Louisiana's Department of Agriculture and Forestry, told reporters last month. "We've never had to fight this many fires simultaneously and at this duration."

A $2,000 reward has been offered for information leading to an arrest by the Louisiana Forestry Association.

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• Louisiana