MOE spokeswoman Kate Jordan says the smell is coming from a Thornton Road composting site owned by Courtice Auto Wreckers.

The facility, which opened in December 2007, is under contract with the City of Toronto to accept its green bin waste.

"We suspect the main source of the odour is that the biofilter on the site isn't operating properly," Ms. Jordan said. A biofilter is used to control odours.

MOE granted the facility a certificate of approval last year, which is like a business licence that lays out terms and conditions to ensure there is no negative impact on the environment.

The certificate given to Courtice Auto Wreckers has requirements for air quality, and Ms. Jordan says the malfunctioning biofilter means the company is not in compliance.

MOE officials met with the facility's owner on March 3, and ordered him to cease accepting waste until the site is in compliance.

"We hope the company will be co-operative," Ms. Jordan said. "If they're not, we have other compliance tools we can use."

Ministry officials will be back to check on the site and will also be monitoring calls and complaints from the public.

The facility's owner, Harvey (Skip) Ambrose, did not respond to requests for comment.The MOE's actions can't come too soon for local residents and businesses, who have been gagging on the smell since the facility opened.

"It's a very noxious odour, it smells like rotting food," said Dr. Sue Dorland, who works nearby at the Oshawa Animal Hospital on Taunton Road. "Our air exchangers bring it inside and we've had staff complaining of headaches, abdominal discomfort and nausea. It has to stop. There's no way we can continue like this."

Dr. Dorland said the smell typically surfaces several times a week and sticks around anywhere from half an hour to several hours.

Also fed up is Nancy Walsh, who lives on Deer Valley Drive, near the Oshawa airport.

She thought the facility was for recycling, and was surprised to learn compost was causing the smell.

"It just smells like you have a bag of garbage in the summer that you left in the back of your garage for awhile," she said. "The other night I was out walking and I had to cut my walk short, I had asthma that was acting up."

City officials are also aware of the problem, but say it falls under the Province's jurisdiction.

"We started getting complaints in December," Mayor John Gray said. "It seems to be quite a widespread area that is affected by the smell." "Unfortunately, there isn't a lot the City can do. Right now this is in the Ministry's hands."

-- With files from Moya Dillon