A company operating a pipeline that dumped more than 800,000 gallons of oil into a southern Michigan river said Wednesday that it is doubling its workforce on the containment and cleanup effort.

Officials with Calgary, Alberta-based Enbridge Inc. made the announcement during an update on the spill, which coated birds and fish as it poured into a creek and flowed into the Kalamazoo River, one of the state's major waterways.

"We've made significant progress," company CEO Patrick D. Daniel said. "But we still have a long way to go in terms of cleanup."

The company had about 200 employees and contractors working on the spill on Tuesday. The Environmental Protection Agency also is bringing in additional contractors, and there was no update on a possible cause, cost or length of cleanup.

"The longer oil is out there the more continued volatilization occurs and the more we become concerned about prolonged potential exposures," said Ralph Dollhopf of the EPA. He said EPA scientists are taking air and water samples.

Health officials say the area is highly toxic and are advising people to stay away. All portions of the Kalamazoo River affected by the spill are closed to fishing, boating and swimming.

Michigan Gov. Jennifer Granholm has declared a state of disaster in Calhoun County and some other affected areas along the river, which eventually bisects the city of Kalamazoo and empties into Lake Michigan at Saugatuck.

Granholm toured the area by helicopter Tuesday night and said she wasn't satisfied with the response to the spill. The leak in the 30-inch pipeline, which was built in 1969 and carries about 8 million gallons of oil daily from Griffith, Ind., to Sarnia, Ontario, was detected early Monday.

Officials don't believe oil will spread past a dam at Morrow Lake, upstream of Kalamazoo.

"We don't want to clean up in the lake," Dollhopf said. "We want to hold it before it gets to the lake."