An Illinois agency has begun recovery efforts at Rock River, where tens of thousands of fish suddenly died on the same weekend as an explosive train derailment in northern Illinois.

A 114-car train carrying ethanol left the tracks Father's Day weekend and some cars blew up. The Illinois Environmental Agency are testing to find out if ethanol spilled into a nearby creek, killing the fish downriver.

The Illinois Department of Natural Resources has already stocked more than 50,000 young smallmouth bass in the river and plan to stock and relocate more commercial and recreational fish.

Preliminary data released Tuesday say biologists conservatively estimate that over 72,000 game and commercial fish died.