PASCAGOULA, Miss. (AP) — Authorities are investigating the cause of an early Friday explosion and fire at a southern Mississippi refinery that killed one worker and injured another.

Allan Sudduth, spokesman for Chevron in Mississippi, said the incident happened in the Cracking II Processing Unit around 2 a.m. Sudduth said the damage was to the furnace in the processing unit.

"There was a detonation and fire in that unit," Sudduth said.

The cracking area of the refinery is the first step in breaking down crude oil into various components so it can become gasoline or coke. It's a hot process and furnaces are involved.

"We are on the scene right now assessing it and we are cooperating with local, state and federal employees," Sudduth said. "That's part of our response plan."

Sudduth said the family of the person who was killed has been notified and the person's name was to be released later Friday. Sudduth said the dead man was a Chevron employee and not a contractor.

Sudduth said a second worker was injured during the incident and was treated at the scene and released. He said all other employees have been accounted for.

About 30 firefighters and police officers responded to the overnight fire. Many of them remained at the front gate, just in case Chevron's fire teams needed assistance.

Jackson County Emergency Services Director Earl Etheridge said fire units from Pascagoula, Jackson County and the Forts Lake Volunteer Fire Department responded to offer backup support to Chevron's fire crews and that all the flames have been extinguished.

"We have a response plan in case of an incident at Chevron and we followed that plan," Etheridge said. "All we do is supply support and protect outside the fence line."

Etheridge said Chevron's response crew determined there's no additional danger to the surrounding community.

"They did some air monitoring for us and determined there's not going to be an environmental impact outside the area where the fire was, so there's no threat to the water or public," he said.

The Pascagoula facility is Chevron's largest wholly-owned refinery. It has a workforce of 1,610 and processes up to 330,000 barrels per day of crude oil to produce gasoline, jet fuel, diesel and other products. The company has operated in Pascagoula for 50 years.