Additionally, BP was ordered to take samples from pipeline walls and photograph pipeline solids to determine if the integrity of the pipeline is sufficient for inspection by an instrument "pig," a device that moves through a pipeline making measurements of wall thickness to detect corrosion. Corrosion in the pipeline caused a crude oil spill last March.

"These additional corrective measures are needed to assure the safety of pipeline operations," PFMSA administrator Tom Barrett said in a press release.

The July 20 order, issued by James Reynolds in the agency's Office of Pipeline Safety, had been expected following July 7 meetings in Alaska between Barrett, other PFMSA officials and BP.

PFMSA had ordered BP to do the smart pig inspection and additional ultra-sound testing in March, but the pig inspection was delayed due to a buildup of sludge. All other work ordered by the federal agency in March has been completed, the agency said.

In a related development, the U.S. Department of Justice has requested samples of fluids from the damaged pipe section and a sample of pipe metal or section of the pipe itself. The fluids have been sent to DOJ investigators, but BP is still working out details of how the pipe section or metal samples can be provided, sources in Alaska state agencies said.

The March break in the 34-inch pipeline resulted in an estimated spill of up to 267,000 gallons of crude oil on the tundra. Cleanup operations are complete and final estimates of the amount of spilled oil are still being done by the state Department of Environmental Conservation. BP spokesman Steve Reinhart said the company has made plans to replace the damaged pipeline and has ordered pipe and other materials.

Tim Bradner can be reached at