Story highlights Arkansas tells pipeline owner Exxon Mobil to preserve documents on the spill

Oil spilled into a Mayflower, Arkansas, subdivision from a gash in the pipeline last week

Families evacuated about two dozen homes as oil crawled through yards and down streets

The pipeline carries Canadian crude from Illinois to Texas

The Arkansas attorney general is opening an investigation into what caused last week's pipeline rupture that allowed thousands of barrels of heavy crude oil to flow into a residential area.

Attorney General Dustin McDaniel said Tuesday he asked Exxon Mobil, the owner of the 60-year-old Pegasus pipeline, to preserve all documents and information related to the spill and cleanup efforts.

"This incident has damaged private property and Arkansas's natural resources. Homeowners have been forced from their homes as a result of this spill," McDaniel said in a news release Tuesday. "Requesting that Exxon secure these documents and data is the first step in determining what happened and preserving evidence for any future litigation."

About two dozen homes in Mayflower, in central Arkansas, were evacuated Friday as the crude oil, which originated in Canada and was bound for Gulf Coast refineries, crawled through yards and down streets spilled from a 2- or 3-inch gash in the underground Pegasus pipeline, officials have said. The evacuation could last for several more days as crews work to clean the spill.

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Mayflower resident Amber Bartlett, who left her home after the spill, told CNN on Tuesday that a cul de sac in her neighborhood last week was "just covered ... nothing but oil."

"It looked like a river flowing down the road," she said.

Bartlett said her yard wasn't affected as badly as others -- "a little bit of oil got just in the very front of the front yard," she said. But the smell is "very intense."

"I went back in for a few minutes to get some things yesterday, and (the smell) ... was more intense than it was on Saturday," Bartlett said Tuesday.

Asked if she had been worried that the underground pipeline could leak, Bartlett said she hadn't even known it was a possibility.

"I can't say that I was concerned, because I do not recall being told that it was there," she said.

The Pegasus pipeline carries Canadian crude from Illinois to Texas, a state transportation engineer said.

Exxon Mobil met with displaced residents over the weekend to explain how they can make claims for losses. "If you have been harmed by this spill then we're going to look at how to make that right," Exxon Mobil Pipeline Co. President Gary Pruessing told them.

Resident Darren Hale complained to CNN affiliate KHTV on Saturday that being forced to leave his home was frustrating.

"I've heard three contradictory answers as to when I will be able to go back home," Hale said. He was first told it would be two days, but later that it would be up to two weeks, he said.

An around-the-clock cleanup operation began Saturday, with workers scrubbing streets and driveways in the Northwood subdivision, CNN affiliate KATV reported

None of the estimated 12,000 barrels of oil that spilled has made it to nearby Lake Conway, a local drinking water source, Faulkner County Judge Allen Dodson told KATV Sunday said.

Bartlett told CNN on Tuesday that Exxon "has been great in aiding the residents in information."

She and other residents still are in shock, she said.

"I think there are probably some homes that will not be livable, which that makes the rest of us in the neighborhood wonder about the value of our homes," she said.