Two workers severely injured in an explosion at a Mississippi processing plant have died, authorities confirmed.

The explosion happened Monday at the DAR PRO Solutions plant at the Greater Jackson Industrial Park near Byram.

William Jackson, 51, of Vicksburg, and Terrence Fortenberry, 56, died from complications of thermal burns, Hinds County Coroner Sharon Grisham-Stewart said Friday. Both men were in the burn unit at Merit Health Central hospital following the explosion. Jackson died Thursday evening and Fortenberry, whose hometown was not released, died Friday morning, the coroner said.

DAR PRO Solutions is a recycling plant that collects and recycles cooking oil and meat byproducts, which is commonly used in the manufacture of dog food, according to its website.

Local authorities, including the Hinds County Sheriff’s Office and the city’s fire and police departments, were unaware an incident occurred at the facility, The Clarion Ledger reported. An official at the plant, Scott Brown, declined to release any details but confirmed an internal investigation is being conducted.

The Occupational Safety and Health Administration cited DAR PRO for three “serious” violations in 2017. OSHA said a fixed ladder on a plant silo was “not maintained in safe condition” and cited the plant for violations with a mechanical power apparatus and a powered industrial truck. The company settled with the agency for $12,604, OSHA said.