ST. LEON, Ind. -- Interstate 74 was backed up in both directions for miles Friday morning after a crash involving hazardous materials in far southeastern Indiana.

Indiana State Police Sgt. Noel Houze said the crash happened in a construction zone in the eastbound lanes at mile marker 159 in Dearborn County.

A tanker truck that was hauling 4,000 gallons of phtalic anhydride molten tipped and overturned, spilling some of its load.

The truck's driver, Andrzej Grela, of Chicago, told police that the load became unstable on uneven pavement and began to shift in the tanker, causing him to drive off the side of the road and into a concrete barrier.

"It is believe that approximately five to 10 gallons have spilled, and the spill has been contained," Houze said.

Police were told that the chemical was more than 300 degrees and that it solidifies and is more stable when it hits 270 degrees.

"The preliminary plan is to allow the substance to cool and solidify, which will make it easier and safer to recover," Houze said.

Westbound lanes were reopened at about 1:30 p.m. Eastbound lanes weren't reopened until 7 p.m.