Ducks are dying at the Metro Wastewater treatment facility in Denver and officials want to know why.

Over the past two weeks 200 ducks have been found dead in the treatment plant's chlorine contact basin and wastewater officials have summoned the help of the Colorado Division of Wildlife and U.S. Fish and Wildlife Service to help figure out what's happening.

"We have something strange going on," said Steve Frank, spokesman for the Metro Wastewater Reclamation District. "That facility has existed for 20 years. No one I know here has ever seen anything like this before. We are asking why here and why now."

Security officers are regularly firing pistols with blanks to scare the ducks from the basin while biologists try to figure out what is happening, he said.

Wastewater officials are considering placing a net over the basin.

"We took immediate action because protecting the environment, including wildlife, is among our top priorities here at Metro," said Director of Environmental Services Steve Pearlman.

Colorado Division of Wildlife officers have taken several specimens to the state's veterinary lab to run tests to try determine the cause, Frank said.