PLAINFIELD, Ind. (AP) — Crews continued working Thursday to douse hot spots at a Walmart warehouse distribution center near Indianapolis, a day after a fire swept through the sprawling building and produced a smoke plume so large it was spotted by a weather satellite.

Plainfield Fire Chief Brent Anderson told reporters at the scene just west of Indianapolis that the fire had been contained and crews rotated every four hours overnight to battle hot spots in the middle of the fire-damaged building, which was still producing smoke.

Anderson said crews would continue to fight the fire through the remainder of Thursday and investigators may not be able to get inside until Friday.

“It’s gonna take quite a bit of manpower and work to remove some of the obstacles in our way,” he said Thursday.

The roughly 1,000 employees who were inside the distribution center when the fire began were not injured, but one firefighter suffered minor injuries fighting the blaze.

The National Weather Service posted a satellite loop on Twitter showing that the black pillar of smoke produced by the fire was visible Thursday in satellite imagery.

The Bureau of Alcohol, Tobacco, Firearms and Explosives is investigating the fire’s cause. Officials said the investigation into the fire’s cause and origin could take days, even weeks.

The Indiana Department of Environmental Management and the U.S. Environmental Protection Agency were testing for hazardous materials and air quality issues from the fire.