The EPA is testing water and soil samples near a northern Indiana pit.

A contractor digging a pit for a sewer pumping station dug through a layer of clay soil last week and exposed a mixture of water and a petroleum-based chemical.

Preliminary results showed that the mixture tested positive for PCBs, a liquid coolant banned by the federal government in 1977 and classified as a probable cause of cancer.

The U.S. Environmental Protection Agency has conducted extensive soil and water testing from the site near Lake Bruce in Rochester, about 40 miles south of South Bend. The agency expects to receive test results later this week.