(SBT24/7News) U.S. 31 remains closed Tuesday morning, and a detour set up through Argos is still in effect, following an accident by two semi-trucks at 12:45 p.m. Monday.

Marshall County Sheriff’s Department records showed a late-night entry Monday that the U.S. Environmental Protection Agency was on-scene, testing for after-effects of the release of liquid petroleum gas in the accident.

Tuesday morning, the Indiana State Police confirmed that one of the trucks was hauling liquid natural gas, specifically cryogenic liquid. The tank ruptured in the crash.

Officials evacuated residents in an approximate half-mile perimeter of the accident, which took place on U.S. 31 near the railroad track just north of 14th Road near Argos.

Police said in the entry the EPA’s test findings will determine how soon the evacuees can return home.

Southbound lanes of U.S. 31 are expected to remain closed for about three days, officials said, and the northbound lanes could open sooner.

The accident occurred in the southbound lanes, police said, when the gas truck slowed to a stop in the right lane for the approaching railroad track. The second truck, also southbound, struck the stopped tanker.

William Merchant, 47, of Hopkins, Mich., the driver of the second truck, was pinned inside his cab for several hours until emergency responders could extricate him. He was airlifted to Memorial Hospital in South Bend. His condition was not immediately known Tuesday morning.

The driver of the stopped truck, Ennis Lester, 65, of Amarillo, Texas, was not seriously injured.

The force of the impact caused the stopped tanker to begin leaking. Initially, officials thought the hazardous material was anhydrous ammonia. Later, they determined it to be cryogenic liquid.

Additional updates will be posted as soon as they become available.