BAY CITY, Mich. — Federal prosecutors say new evidence caused them to drop charges against two people accused of intentionally discharging oily water into Lake Huron from a tugboat in 2014.

Spokeswoman Gina Balaya (Buh-LYE’-uh) says it was in the “best interests of justice” to drop the case against engineer Jeffrey Patrick and assistant engineer William Harrigan. She didn’t describe the new evidence.

A trial was supposed to start Tuesday in Bay City federal court, but a judge dismissed the case last week.

The oily sheens in Lake Huron were spotted by air, east of Cheboygan and east of Alpena, in 2014. Patrick and Harrigan were charged with conspiracy and another crime while aboard a boat called Victory.

Messages were left seeking comment from defense lawyers.