A mechanical failure at Denver International Airport sent up to 1 million gallons of raw sewage and industrial wastewater into creeks and canals flowing toward the Barr Lake fishery and bird sanctuary.

Airport spokesman Jeff Green says the spill appears to have started about 7 p.m. Tuesday when a pump malfunctioned. Maintenance crews made the discovery Wednesday morning. The reason for the malfunction is unclear.

Tri-County Health Department environmental health director Tom Butts says it wasn't immediately clear whether any contamination made it off airport property.

Airport, state and county health officials were testing Barr Lake and the waterways that flow into it to determine if there is a health or environmental threat.