Traffic on Interstate 95 was snarled after an 18-wheeler carrying phosphorous overturned near Ridgeland early Friday, according to Ridgeland Police.
The wreck occurred when the truck's driver, Ralph Bauer of Anadulsia, Ala., fell asleep behind the wheel, crossed into the median and struck the cable barrier, authorities said.
The impact caused the truck to turn over on its left side, spilling a load of phosphorous onto the roadway.
The truck driver was not injured, a police department spokesman said.
Though not hazardous, clean up on the highway was expected to last into Friday night, according to police.