Prime Minister Stephen Harper said Thursday he expects better from the large oil companies who are ultimately responsible for the protection of the environment and surrounding wildlife near their work sites.

The comments come two days after 500 waterfowl were poisoned after they landed in a toxic Syncrude tailings pond.

"It's obviously a terrible tragedy and I think we and a lot of people are upset about it," he said. "I think we expect better to be quite honest. This kind of thing shouldn't be happening."

The company said two of the surviving birds have died. Only three of the estimated 500 are still alive.

Harper said the federal government will strengthen environmental enforcement legislation in the upcoming months.

"We have something that should have been prevented at least in my judgment," he said. "There are supposed to be systems in place to prevent this particular kind of event and obviously we're greatly disappointed."

Syncrude Canada Ltd. became aware of the disaster Monday after a tipster called the company -- and the Alberta government -- to tell them a large flock of birds landed in the tailings pond.

The tailings ponds contain leftover water is dumped in the tailings ponds, which contain a mixture of clay, sand water and hydrocarbons. Any birds that land in the water would come out greasy, oily and unable to fly, experts say.

The ponds are supposed to have measures in place that keep migrating waterfowl from landing on the ponds, such as scarecrows and noisemakers.

Three poisoned birds were flown to Edmonton early Tuesday by Syncrude. The ducks were initially taken to a downtown emergency veterinary hospital for an initial check-up and then transferred to the Wildlife Life Rehabilitation Society of Edmonton.

Another two birds were captured by Syncrude Tuesday and were supposed to also be flown to Edmonton, but they died before making the trip.

Alberta Environment said it is investigating whether Syncrude had a waterfowl protection plan in place. If the company did not comply, the Alberta government could take action, with penalties up to $1 million.

The sheer number of wildlife killed in the incident has led to the story spreading all over the world, leading to criticism from all side.

Imperial Oil CEO Bruce March said from his Calgary office said there are no excuses for the accident.

"It was unfortunate, tragic, deeply disappointed, (it's) something that hasn't happened in a long time," he said.

Alberta's opposition Liberals accused the province of holding back pictures from the tailings pond where the ducks died.

"Why the coverup?" Liberal Leader Kevin Taft said. "Why won't he just release these photos?"

Syncrude is located about 40 kilometres north of Fort McMurray.

With files from Joel Gotlib