More than 400 fish have died this week in the downtown-Meadville waters of Mill Run. That’s the bad news — and, in one way, it’s the good news, too.

Officials at Meadville’s Pennsylvania Department of Environmental Resources office are seeking the public’s help in solving the mystery. Ironically, their large, four-story office building is also downtown, at the corner or Market and Chestnut streets, and it sits quite near to a visible stretch of the stream that feeds into French Creek about a quarter-mile farther downstream.

Mill Run originates east of town, near Tamarack Lake, and travels through three miles of city terrain, most of it unseen as it meanders beneath downtown streets.

A DEP employee leaving the building on Tuesday noticed some of the dead fish and saw that the slowly-flowing water had a strange blue-green color at that spot.

Something entered the creek, contaminating the waters, officials report, but they don’t know exactly what or where. So much of the creek is underground that the entry point will be difficult to find.

DEP staffers have done some preliminary investigation, however, and a 1,000-foot stretch between the new Walgreens drug store (at Liberty and North streets) and Meadville Public Library (at North and North Main), seem to be strong possibilities for the contamination’s point of origin.

Some people have reported smelling an odor that could be an indicator of the trouble, but DEP officials have not detected it themselves.

It is not yet known what substance caused the water’s blue-green color.

The 400 fish represent various species, and some of the fish were somewhat surprising to DEP officials. “We were happy to see the diversity of the fish we have found so far. It says good things about Mill Run. Many of the ones we found need to live in extremely clean environments,” said Freda Tarbell, DEP community relations coordinator.

The find indicates that “Mill Run contains a good, healthy aquatic community,” she said, with waters that are generally very clean. In fact, a species of sculpins and at least three species of darters that were found all require extremely clean environments to survive.

Anyone with information about the contamination problem is asked to call 332-6816.