UPDATE 1-US orders Exxon to craft pipeline safety plan
* Government mandates safety plan for restart
* High river levels hampering investigation of cause
* Refinery at "minimum rates" until secure other supply (Recasts story to adds government order to make safety fixes)
WASHINGTON/HOUSTON, July 5 (Reuters) - U.S. pipeline safety regulators on Tuesday said Exxon Mobil (XOM.N) must make fixes to its ruptured Montana oil pipeline and submit a restart plan before oil can flow again.
The U.S. Transportation Department's Pipeline and Hazardous Materials Safety Administration also ordered the company to re-bury the pipeline segment and do a risk study where it crosses any waterway.
"The safety of our nation's pipelines is a priority and the investigation into this incident is ongoing," Transportation Secretary Ray LaHood said in a statement, noting that those found responsible would be held accountable.
Exxon Mobil does not have a definite repair plan yet for the ruptured Montana crude oil pipeline that it shut over the weekend, and company and government officials are still trying to determine the cause of the spill, a top executive said earlier on Tuesday.
Oil deposits from the rupture may have traveled as far as 240 miles downstream, the government said in its order.
The company and state and federal investigators are "working in parallel, looking at both the investigation, trying to determine what happened, as well as possible repair plans," Gary Pruessing, president of Exxon Mobil Pipeline Company, told reporters in a briefing.
"We do not yet have a definitive plan on when we will be able to restart the line," he said.
Exxon estimated that up to 1,000 barrels (42,000 gallons) of oil spilled into the rain-swollen Yellowstone River when its Silvertip crude oil pipeline ruptured late Friday. Exxon said it shut the 40,000 bpd pipeline early Saturday within seven minutes of discovering a pressure loss that indicated a rupture.
High, rushing water in the river was hampering the probe, but Pruessing said the company hadn't confirmed any soiled areas beyond 25 miles downriver.
"River levels continue to be very high, the river is very strong, that does become something we need to consider in trying to get at the actual site where the incident occurred," Pruessing said.