An Exxon Mobil crude oil pipeline ruptured near the town of Mayflower in the US state of Arkansas, spilling thousands of barrels of oil, the company said.
Exxon shut the 50-centimetre Pegasus pipeline, which carries crude oil from Pakota, Illinois, to the Gulf Coast, after the leak was discovered on Friday afternoon.
Exxon, which was hit with a $1.7m fine by regulators this week over a 2011 spill in the Yellowstone River, said a few thousand barrels of oil had been observed.
Local media reported the spill occurred in a subdivision, and Mayflower police said the oil had not reached the nearby Lake Conway.
Federal, state and local officials were on site and the company said it was staging a response for a spill of more than 10,000 barrels "to be conservative."
"The air quality does not likely present a human health risk, with the exception of the high pooling areas, where clean-up crews are working with safety equipment," Exxon said in a statement.
Keystone XL pipeline
The US Environmental Protection Agency had categorised the rupture as a "major spill," Exxon said, and 22 homes were evacuated following the incident. Clean-up crews had recovered approximately 4,500 barrels of oil and water.
The spill occurred as the US state department is considering the fate of the Keystone XL pipeline, which could carry 800,000 barrels of crude per day from Canada's oil sands to the Gulf Coast.
Environmentalists, concerned about the impact of developing the oil sands, have sought to block its approval. Supporters say Keystone will help bring down the cost of fuel in the United States.
The Arkansas spill was the second incident this week where Canadian crude has spilled in the United States. On Wednesday, a train carrying Canadian crude derailed in Minnesota, spilling 15,000 gallons of oil.