BILLINGS, Mont. -- Exxon Mobil Co. reassured concerned regulators that an oil pipeline beneath the Yellowstone River was buried deep enough and not in danger just a month before it broke in a flood and spewed an estimated 1,000 barrels of crude into the waterway.
Details about Exxon Mobil's actions leading up to the Friday night spill into one of the West's premiere rivers emerged in federal safety documents as cleanup work continued downstream of the rupture site in the Montana town of Laurel.
There is still no definitive word on how far downriver the spill could spread. Oil has been reported as far as 240 miles away and officials worry high water could wash it into new areas.
There were also new revelations that Laurel officials pressed Exxon Mobil about the integrity of the line as the river rose, but were reassured it was safe.
The cause of the pipeline failure remains under investigation. The prevailing theory is that the raging Yellowstone eroded the riverbed and exposed the line to damaging debris.
Documents from the Department of Transportation show it took Exxon Mobil almost an hour to fully seal the pipeline after the accident -- nearly twice as long as it had publicly disclosed. It was not immediately clear if the change could alter the estimate of crude released into a river famous for its fishing and vital to farmers for irrigation.
"The best thing they could do at this point is be completely honest," said Gov. Brian Schweitzer. "It is clear that their veracity has not been 100 percent to this point."
Company representatives initially said it took "at most" a half hour to stop the flow, then later said took just six minutes to shut down the pipeline.
On Tuesday, Exxon Mobil Pipeline Co. president Gary Pruessing said in response to a question from Schweitzer that it took 30 minutes to seal off all the valves needed to stop the flow of crude into the river.
But Department of Transportation records indicate the pipeline was not fully shut down for 56 minutes after the break occurred Friday near Laurel at 10:40 p.m. local time. Emergency responders at the National Response Center were notified of the spill at 12:19 a.m.
The company hasn't responded to Associated Press requests for a timeline.
An Exxon Mobil spokesman said the longer time span was based on information provided to the agency by the company and the discrepancy might have come about because Exxon Mobil Pipeline Co. President Gary Pruessing was speaking without any notes in front of him when he addressed Schweitzer.
"Clearly our communication with the regulator (DOT) is the one that we've got precision on," spokesman Alan Jeffers said.
It was not the first time the company offered clarification of its response and assessment of the spill. A day earlier, the company acknowledged under political pressure that the leak's impact could extend far beyond a 10-mile stretch of the river it initially said was the most affected area. The company had earlier downplayed government officials' assertions that damage was spread over dozens of miles.
The river has been flowing too swiftly for crews to reach some oiled areas, and forecasters said mountain snowmelt was adding to high water levels. Officials speculated that the surge may push oil into areas that haven't yet been damaged.
Most observations have been made through aerial flights.
A few miles downriver from the broken pipe, homeowner Robert Castleberry said he had been out of his house since Saturday because of dangerous fumes from oil that the river pushed across his yard and into the crawlspace beneath his house.
Castleberry's wife suffers from heart disease and the fumes caused her breathing difficulties, he said. While he appreciated the company promising to cover the couple's immediate expenses, the retired fuel truck driver was doubtful workers would be able to clean up the black, gooey film that laced through the underbrush along the river.
"Exxon's been nothing but 100 percent with us," he said. "But when you get into brush that thick, that's going to be virtually impossible to clean."
Company and federal officials said they have only seen oil about 25 miles downstream from the site of the break near Laurel. But Schweitzer said he believes some has traveled hundreds of miles to North Dakota.
"At seven miles per hour, some oil is already in North Dakota. That's a given," Schweitzer said. "I'm asking everyone to get out there and report what you see on the river."
Representatives of Exxon Mobil and the Environmental Protection Agency said they had no reports of oil beyond the town of Huntley, about 24 miles downstream.
Transportation officials said Tuesday that oil was observed as far downstream as 240 miles in Terry, Mont. The agency said that information was provided by Exxon Mobil, but company spokesman Alan Jeffers said he was not aware of any such sighting.
To broaden its search for the oil, Exxon planned to test whether the river was safe to navigate with a jet-powered boat, with eight more on standby if the launch was successful, Glass said.
Federal regulators have ordered Exxon to make safety improvements to the 20-year-old pipeline. Among them was an order to re-bury the line to protect against external damage and assess risk where it crosses a waterway, which the company intended to comply with, Jeffers said.
"We will follow their requirements," he said.
The company also will have to submit a restart plan to the Department of Transportation before crude can again flow through the line.
Schweitzer also ordered a review of pipelines that cross major and minor rivers in the state. Officials will look at the pipes' age, location of shut-off valves and whether they are similar to the ruptured pipe. He said the state has 88 such crossings.
Modern pipelines can be buried as much as 25 feet beneath bodies of water; Exxon Mobil's Silvertip line was 5 to 8 feet below the bottom of the Yellowstone.
The line was temporarily shut down in May after Laurel officials raised concerns that it could be at risk as the Yellowstone started to rise. The company restarted the line after a day, following a review of its safety record.