A North Dakota regulator says moving crude oil through a pipeline is the safest transportation mode available.

"But even with the safest forms of transportation, accidents do happen," Public Service Commissioner Tony Clark said. "When they happen, they tend to be very bad."

A fire late Wednesday along the Enbridge Energy Partners LP Lakehead pipeline in northern Minnesota, which carries crude oil from Saskatchewan to the Chicago area, killed two repair workers.

"Clearly, our company is very shaken up about this," Enbridge spokesman Bill Stephens said Thursday. "Any accident is inexcusable and terrible.

"To transport crude to get to people who need the energy and to keep up with a growing market, pipelines are the most efficient and safest way to do it," he said.

The Enbridge pipeline company runs a pipeline that carries crude from oil fields in North Dakota and eastern Montana to refineries in Minnesota. Enbridge Pipelines North Dakota LLC is part of Enbridge Inc. of Calgary, Alberta.

The company says it is wrapping up a $40 million project to increase pipeline capacity in North Dakota to keep pace with increased crude oil production.

The pipeline's capacity is being raised 30,000 barrels daily to 110,000 by adding pump stations and increasing pressure in the line, the company said. The project is slated to be completed by the end of the year.

A second expansion, pegged at $150 million, will add 51,000 barrels from Minot to Clearbrook, Minn.

- Associated Press