MOUND — Two Louisianians were killed and a third person remained hospitalized this morning after a fiery crash on Interstate 20 near Mound Wednesday afternoon.

Carlos Jones, 64, and Susanne Jones, 60, both of Bogalusa, were pronounced dead at the scene by the Madison Parish Coroner’s Office. John Meshell, 35, of Strong, Ark., was in critical condition at University Medical Center in Jackson.

Louisiana State Trooper Jessie Wells said the wreck occurred when a westbound 18-wheeler tanker-truck carrying heating-oil residue crashed into the back of a Louisiana Department of Transportation road grader that was on the side of the four-lane highway. The truck, driven by Meshell, then careened across the median and hit an eastbound pickup carrying the Joneses.

The tanker and the pickup, which had been pulling a camper, burst into flames almost immediately after impact, Wells said. Both Joneses were pronounced dead at the scene, Wells said.

“We know what happened, but we just don’t know how it happened,” said Wells. He said it was not clear what work the road machinery was performing or why the driver lost control.

The interstate was closed in both directions for two hours while emergency personnel cleared the scene after the roaring blaze was extinguished.

Six fire departments and about four other agencies responded to the crash.