An investigation was underway Monday into what caused an earth-shaking explosion and fire Sunday night at a diesel fuel plant in Norco.

St. Charles Parish crews responded to the Diamond Green Diesel plant about 9:30 p.m. after a production unit blew up.

The unit was shut down and the fire was allowed to burn itself out, authorities said.

Jean Kelly, a spokeswoman for the state Department of Environmental Quality, said the fire was out by about 12:10 a.m. Monday.

No one was injured, and all employees were accounted for. No safety precautions were issued, and air-monitoring crews found nothing detectable, according to parish and state officials.

“I think we’re in good shape,” Kelly said of the incident and any possible effects it might have had on the area.

She said DEQ personnel will visit the site again to make sure there was no environmental damage, though she could not say exactly when.

The plant, a joint venture between Diamond Alternative Energy LLC, a subsidiary of Valero Energy Corp., and Darling International Inc., processes used cooking oil and other feedstocks into renewable diesel fuel.

Taryn Rogers, a spokeswoman for the plant, said the fire did not affect operations at the facility, which is in the 14000 block of River Road.

“The safety of our employees and community, as well as the protection of our environment is of the utmost importance,” Rogers said in a prepared statement.

Follow Danny Monteverde on Twitter, @DCMonteverde.