An official with Environment Canada confirmed Wednesday that the agency has launched a federal investigation into Halifax's broken sewage treatment plant.

York Friesen, director of the Environmental Protection Branch for the Atlantic Region, told CBC News that his department began its investigation in April after it received complaints from the public.

Friesen said his department's mandate is to look at the impact the raw sewage is having on the health of local fish stocks. He said investigators also want to know what caused the sewage treatment plant to fail.

Raw sewage has been flowing into Halifax harbour since January when the $54-million sewage treatment plant malfunctioned, causing the station to overflow with raw sewage.

Two weeks ago, the situation worsened after the screens that prevent solids – also known as floatables – from entering the harbour were removed from the sewer outfalls. Municipal staff said the buildup was causing damage to the machinery.

The municipality was forced to revive cleanup sweeps along beaches to pick up the floatables such as tampon applicators and condoms.

At the end of April, the federal Environment Department ordered the Halifax Regional Municipality to take steps to reduce the amount of sewage being dumped into the harbour.

"They do need to provide us with regular reports on what they are doing to mitigate the flow, every 30 days, I believe," Friesen said.

Several municipal councillors told CBC News on Wednesday they were informed of the federal environmental investigation during a closed-door meeting on Tuesday.

During the three-hour meeting, municipal staff presented council with several options to temporarily fix the sewage problem.

The councillors said the municipality must present a formal plan to Environment Canada to prove they are dealing with the sewage issue as quickly as possible.

The Halifax sewage treatment plant is not expected to back in operation until next spring.

Friesen said fines for violating the fishery provisions of the Environment Protection Act range from $300,000 to $1 million.

A public report on the situation is supposed to be issued before the end of the month.