MERRILLVILLE, Ind. — About 20 acres (8 hectares) in Northwest Indiana burned after flames spread from an open burn pit into surrounding fields fields, a fire chief said.

The fire Thursday afternoon in Merrillville took nearly two hours to be brought under control by firefighters from eight departments, Merrillville Fire Chief Ed Yerga said.

No injuries were reported and the fire did not spread to any structures or vehicles, The (Northwest Indiana) Times reported.

Yerga said the fire was caused by a homeowner burning things in a backyard.

“Open burning is prohibited in Merrillville; residents need to burn fire wood in containers for recreational use only,” Yerga said. “During this time of year, they also need to pay attention to the weather. In 30 mph winds, wind can easily carry flames or embers from a small fire into fields and create a massive brush fire. The ground dries out pretty quickly.”

The fire sent thick smoke into southbound lanes of Interstate 65.

Yerga warned against discarding lit cigarettes on the ground.

“It happens off I-65 when people flick cigarettes off into the brush and fires are started,” Yerga said. “It’s dangerous. Wildfires are the No. 1 killer of firefighters.”