BAYTOWN, Texas (Reuters) - Exxon Mobil Corp brought under control a fire that erupted on Wednesday at its Baytown, Texas, refining and chemical plant complex, injuring 37 workers, none seriously.

Emergency crews worked to extinguish the fire into the evening, the company said in a statement. The cause of the blaze was not disclosed, but an investigation was under way and Exxon said it was cooperating with authorities.

The injured workers were treated for minor burns, none requiring hospitalization, plant manager Jason Duncan told a news briefing.

The fire, which was put down by the company’s employees, sent black smoke into the air over the complex in Baytown, a city of 75,000 which is located about 30 miles (48 km) east of Houston. Firefighters and equipment from the city entered the plant at midday to assist, an official said.

Firefighters continued to spray water on a charred column where the fire began late Wednesday. Residents around the plant were told to close windows and doors, turn off air conditioning and remain in their homes, schools or offices. A shelter in place order was lifted after several hours.

“We are cooperating with regulatory agencies. We deeply regret any disruption or inconvenience that this incident may have caused the community,” Exxon spokeswoman Sarah Nordin said in a statement.

Available air monitoring information from the inside the Baytown Olefins Plant’s grounds and outside monitoring sources recorded no adverse impacts, she said. The fire burned residual fuel contained in a large column on Wednesday.

The Baytown complex that includes the olefins plant where the fire occurred employs about 7,000 people among four manufacturing sites that cover 3,400 acres (13.8 square kilometers). It sits along the Houston Ship Channel, the nation’s largest and busiest energy port.

Duncan declined to comment on the fire’s impact on production at Exxon’s adjacent 560,500 barrels-per-day oil refinery. Two people familiar with its operations said Exxon reduced some production at the refinery, which provides feedstocks to the unit that caught fire.

Aerial footage during the blaze showed flames and heavy smoke emanating from a large column at the facility, which Exxon identified as part of its production of olefins, a component of plastic. Emergency vehicles and people were massing around the edge of the complex.

The company said a total of 66 staff and contract workers were examined and released during the day at a nearby health clinic which provides first aid.

Exxon last year completed the construction of a multi-billion-dollar ethane cracker at the Baytown Olefins Plant. The cracker can produce 1.5 million tons per year, and provides feedstock to two other production lines at its Mont Belvieu, Texas, plastics plant.