Photo taken on Dec. 23, 2021 shows ExxonMobil Baytown Olefins Plant in Baytown, Texas, the United States. Four people were injured on Thursday morning at ExxonMobil Baytown Olefins Plant in Texas, according to the company. (Photo by Lao Chengyue/Xinhua)

Four people were injured on Thursday morning at ExxonMobil Baytown Olefins Plant in south central U.S. state Texas, according to the company.

The fire, which first responders started to put out around 1 a.m., had been safely extinguished by 9:15 a.m., Exxon said.

Officials are monitoring the air quality but so far no shelter-in-place order has been issued for residents in the area.

Among the injured, two were treated for burns, a third person had a fracture and the fourth person was treated for injuries related to a fall of about 40 feet, said an ABC News report.

Exxon said all the injured were in stable condition.

"All other personnel at the site have been accounted for, and we're ensuring that these individuals are receiving the best care possible," said ExxonMobil refinery manager Rohan David.

It's not immediately known what caused the fire. Enditem

Photo taken on Dec. 23, 2021 shows ExxonMobil Baytown Olefins Plant in Baytown, Texas, the United States. Four people were injured on Thursday morning at ExxonMobil Baytown Olefins Plant in Texas, according to the company. (Photo by Lao Chengyue/Xinhua)

Photo taken on Dec. 23, 2021 shows ExxonMobil Baytown Olefins Plant in Baytown, Texas, the United States. Four people were injured on Thursday morning at ExxonMobil Baytown Olefins Plant in Texas, according to the company. (Photo by Lao Chengyue/Xinhua)

Photo taken on Dec. 23, 2021 shows ExxonMobil Baytown Olefins Plant in Baytown, Texas, the United States. Four people were injured on Thursday morning at ExxonMobil Baytown Olefins Plant in Texas, according to the company. (Photo by Lao Chengyue/Xinhua)