EDMONTON – Environmental groups want to know if the federal government is following its own law and investigating a recent toxic spill from Suncor’s oilsands plant into the Athabasca River.

Their letter to Environment Canada comes after a provincial investigation concluded that the spilled wastewater was toxic to fish.

“It indicates that a violation of the Fisheries Act has occurred,” said Melissa Gorrie of the law firm Ecojustice. “We’re asking the federal government to ensure that they investigate this matter and take action as needed.”

Environment Canada officials couldn’t immediately say what their department’s response to the spill has been. Nor could they offer an immediate response to the letter, which was sent on behalf of Greenpeace, Keepers of the Athabasca, the Council of Canadians, Public Interest Alberta and the Sierra Club.

On March 25, a wastewater pipe at the Suncor plant near Fort McMurray froze and burst open, sending process-affected water into a partially frozen outfall pond containing treated water.

An investigation by Alberta Environment found undiluted samples from the killed rainbow trout fingerlings that had been exposed to it. The investigation concluded that the fish were probably killed by high levels of naphthenic acids, chemicals that occur naturally in bitumen.

The undiluted samples were also found to contain levels of salts and ammonia above provincial guidelines. Metals including selenium, boron and arsenic were found at twice the recommended levels for long-term exposure.

The provincial investigation concluded that by the time the water spilled from the outfall pond into the Athabasca River, it was probably too diluted to pose a health threat to humans.

Still, Gorrie said, the federal government is obliged under the Fisheries Act to investigate any toxic releases into fish-bearing waters. That Act stipulates that any release of such material is an offence, whether or not the waterway is rendered toxic as a result.

She also pointed out that Ottawa is probably well aware of the spill, under an agreement in which Alberta promises to inform Environment Canada of any such events.

The letter gives the government until May 27 to respond.

“It’s something we’re going to continue to monitor,” Gorrie said. “If the federal government doesn’t act, we would consider our options in moving this forward through a different avenue.”

Alberta’s investigation is ongoing and the full lab results from the spill have not yet been released.

Suncor was recently given until the end of April to fix a separate problem with one of its wastewater treatment ponds, which leaked toxins into the Athabasca in March 2011.