Twelve thousand barrels of oil and water have been recovered in continuing clean up operations of the Exxon Mobil pipeline spill that spewed thousands of barrels of Canadian crude in Arkansas.
Clean-up crews had earlier recovered approximately 4,500 barrels of oil and water on Saturday but Exxon had no specific estimate of how much crude oil had spilled.
Exxon spokesman Alan Jeffers said on Sunday that crews had yet to excavate the area around the pipeline breach, a needed step before the company can estimate how long repairs will take and when the line might restart.
"I can't speculate on when it will happen," Jeffers said. "Excavation is necessary as part of an investigation to determine the cause of the incident."
Exxon's Pegasus pipeline, which can carry more than 90,000 barrels per day of crude from Patoka, Illinois to Nederland, Texas, was shut after the leak was discovered late Friday afternoon in a subdivision near the town of Mayflower.
The US Environmental Protection Agency had categorised the rupture as a "major spill," Exxon said, and 22 homes were evacuated following the incident.
Exxon said it staged the response to handle 10,000 barrels of oil "to ensure adequate resources are in place".
Officials from the US Environmental Protection Agency and the Department of Transportation's Pipeline and Hazardous Materials Safety Administration (PHMSA) also were on site to investigate the spill.
Fifteen vacuum trucks remained on the scene for cleanup, and 33 storage tanks were deployed to temporarily store the oil.
The pipeline 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 Inc pipeline last summer kept that line shuttered for around 11 days.
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.