Exxon Mobil on Sunday continued cleanup of a pipeline spill that loosed thousands of barrels of heavy Canadian crude in Arkansas as opponents of oil sands development latched on to the incident to attack plans to build the Keystone XL line.

Exxon's Pegasus pipeline, which can carry more than 90,000 barrels per day (bpd) of crude from Pakota, Illinois to Nederland, Texas, was shut after the leak was discovered late Friday afternoon in a subdivision near the town of Mayflower. The leak forced the evacuation of 22 homes.

The company did not have an estimate for the restarting of the pipeline, which was carrying Canadian Wabasca Heavy crude at the time of the leak. An oil spill of more than 1,000 barrels into a Wisconsin field from an Enbridge pipeline last summer kept that line shuttered for around 11 days.

The Arkansas spill drew fast reaction from opponents of the 800,000 bpd Keystone XL pipeline, which would carry heavy crude from Canada's tar sands to the U.S. Gulf Coast refining center.

Environmentalists have expressed concerns about the impact of developing the oil sands and say the crude is more corrosive to pipelines than conventional oil. On Wednesday, a train carrying Canadian crude derailed in Minnesota, spilling 15,000 gallons of oil.

"Whether it's the proposed Keystone XL pipeline, or ... (the) mess in Arkansas, Americans are realizing that transporting large amounts of this corrosive and polluting fuel is a bad deal for American taxpayers and for our environment," said Representative Ed Markey, a Massachusetts Democrat.

Supporters of Keystone XL and oil sands development say the vast Canadian reserves can help drive down fuel costs in the United States. A report from the Canadian Energy Pipeline Association, put together by oil and gas consultancy Penspen, argued diluted bitumen is no more corrosive than other heavy crude.

arkansas-oil-spill-hoses_65889_600x450.jpg

arkansas-oil-spill-truck_65891_600x450.jpg

Cleanup

Exxon said that by 3 a.m. Saturday there was no additional oil spilling from the pipeline and that trucks had been brought in to assist with the cleanup. Images from local media showed crude oil snaking along a suburban street.

Officials from the U.S. Environmental Protection Agency and the Department of Transportation's Pipeline and Hazardous Materials Safety Administration were deployed to the scene.

"Cleanup efforts are progressing 24 hours a day," said Exxon spokesman Alan Jeffers, who added the oil had not leaked into nearby Lake Conway.

"We were very fortunate that the local responders made sure the oil did not enter the water."