Investigation and cleanup crews remained on duty in Mayflower, Ark., following the March 29 ExxonMobil Pegasus pipeline rupture, which spilled thousands of barrels of Canadian crude and triggered evacuation of nearby homes.

As of April 2, on-site state, federal and corporate officials had not yet determined the cause of the spill and could not predict when it would be repaired or when residents of the 22 evacuated houses could return.

An engineer from the U.S. Dept. of Transportation's Pipeline and Hazardous Materials Safety Administration (PHMSA) reported a 2-in. to 3-in.-long gash in the pipeline.

Built in the 1940s, the Pegasus pipeline carries Canadian crude between Patoka, Ill., and Nederland, Texas. The pipeline's capacity per day is 90,000 barrels, or about 3.8 million gallons.

Issued late on April 1 by a joint information center staffed by state, local and company representatives, a statement said an excavation and removal plan was in development for review by PHMSA. However, no information was provided about when the plan would be submitted, when it might get approval or when pipeline removal and repair work would start.

The statement also said a cleanup plan had been developed but provided no further details.

On April 2, Arkansas Attorney General Dustin McDaniel said his office would investigate the cause and impact of the spill and asked ExxonMobil to retain all documents and other information pertaining to the incident.

The amount of the spill was unknown, but ExxonMobil said it was prepared to handle 10,000 barrels and already had recovered about 12,000 barrels of water and oil.

The U.S. Environmental Protection Agency classifies as "major" any spill of more than 250 barrels.

ExxonMobil was hit on March 25 with a $1.7-million fine by PHMSA as a consequence of a crude-oil pipeline break that contaminated the Yellowstone River near Laurel, Mont., in July 2011.

It could not be determined when the Pegasus pipeline section in Arkansas was inspected last, but ExxonMobil was fined $26,500 for exceeding five years between inspections of a stretch of the Pegasus pipeline that runs under the Mississippi River between Illinois and Missouri.

The Pegasus carries Canadian heavy-crude oil, as would the planned Keystone pipeline now up for approval. Critics claim this oil causes pipelines to operate at higher temperatures, increasing the risk of rupture from corrosion.

In Mayflower, the firm brought in 120 workers, 15 vacuum trucks and 33 storage tanks for temporary use as crews started steam-cleaning and pressure-washing oil from yards and streets.