ExxonMobil says manufacturing defect in pipeline is to blame for its crude-oil spill in Mayflower, Ark.

ExxonMobil is blaming manufacturing defects for the spill that sent 150,000 gallons of crude oil into the small town of Mayflower, Ark., in March. A cracked seam is to blame, according to an independent report conducted by Hurst Metallurgical Research Laboratory Inc., Chuck Bartels reports for The Associated Press. Bartels said Exxon Mobil and the Pipeline and Hazardous Materials Safety Administration declined to release the report to the media. (AP photo from April 1 of water and oil in a drainage ditch in Mayflower)

In a news release ExxonMobil said, "Based on the metallurgical analysis, the independent laboratory concluded that the root cause of the failure can be attributed to original manufacturing defects — namely hook cracks near the seam. Additional contributing factors include atypical pipe properties, such as extremely low impact toughness and elongation properties across the ... seam."

The spill dumped 12,000 barrels of oil on the 2,300-population town, and there was some concern that ExxonMobil didn't respond properly to the spill, with contradictions in its timeline of events. Arkansas Attorney General Dustin McDaniel and U.S. Atty. Christoper Thyer last month filed a lawsuit seeking $45,000 per day in penalties for the effects of the spill, with McDaniel saying the spill itself was a violation of state and federal law, and that it disrupted the lives of the residents of the 22 homes that were evacuated, Bartels reports.