Two people were killed and 10 other injured following an industrial plant accident Monday in Nebraska. Authorities have still not determined whether an explosion occurred inside the International Nutrition plant in Omaha.

The names of the two people killed in the Monday-morning accident were not released, the Omaha World-Herald reported. Ten people were injured in the plant accident, including four who were listed in critical condition.

Omaha Interim Fire Chief Bernie Kanger told the Associated Press that the accident is under investigation, adding that there were no chemicals inside the plant when the incident occurred. He said 38 people were in the plant at the time. As of Monday afternoon, it was unclear whether an explosion occurred at the facility. Rescuers recalled seeing flames and smoke as they responded to the accident.

Concerned about a possible collapse, authorities were trying to secure the building as of 3:10 p.m. At that time, the building had not been cleared, according to the World-Herald.

“It was a very dangerous situation and continues to be very dangerous,” the fire chief said shortly after the accident.

Kanger is scheduled to hold a news conference on the plant accident at 8 p.m. local time.

The International Nutrition plant is not near any other buildings, and no homes had to be evacuated following the incident. Sarah White, whose husband works at the plant, said her husband called her after the accident.

“I could hear the panic in his voice,” she told the AP. “But he said he was OK.”

Nate Lewis, a 21-year-old production line worker at the plant, said the building went “pitch black” after the accident and needed to use his cell phone as a light. He said the sprinkler system then went off and drenched his clothes.

Mary Brown, who has a son who works at the plant, said she texted with her son before he lost cell phone service. “He’s pretty shaken up,” she said of her son, Jake Wolfe.

Among the critically injured was a man who may have suffered hypothermia-like symptoms, according to the World-Herald. He was submerged in cold water after an unknown object fell on him. Other injuries included a collapsed lung and hypothermia.

Monday’s accident was not the first incident at the Omaha plant resulting in injury. A man almost died there in August 2002 when a mixing machine nearly crushed him. The incident led to a $13,600 fine for five “serious” violations – defined as “when the workplace hazard could cause an accident or illness that would most likely result in death or serious physical harm, unless the employer did not know or could not have known of the violation,” according to the World-Herald.

The company was also fined $10,430 for six “serious” violations during a planned inspection.