Cleanup workers prepare to secure absorbent booms on the Kalamazoo river after an oil pipeline leaked oil into the river near Marshall, Michigan July 31, 2010. REUTERS/Rebecca Cook

CALGARY, Alberta (Reuters) - Oil that fouled a Michigan river system spewed from a rip less than five feet long in an Enbridge Inc pipeline, a company executive said on Saturday after crews extracted the ruptured piece.

The pipeline, part of Enbridge’s system that carries most of Canada’s crude oil exports into the United States, ruptured nearly two weeks ago near Marshall, Michigan, and there is still no estimate when it might be restarted.

Looking at the length-wise tear does not provide enough information to determine what caused 800,000 gallons of heavy crude oil to spill into the Kalamazoo River system, said Steve Wuori, president of Enbridge’s liquids pipelines division.

Under the watch of the U.S. National Transportation Safety Board, crews extracted a 50 foot (15 meter) section on Friday and it is being shipped to Washington for analysis, officials said.

“I would think it will be late tomorrow before the replacement section is welded into place,” Wuori told reporters in conference call to discuss the incident.

Authorities must approve Enbridge’s restart plan before it can resume shipping crude on the 190,000 barrel a day pipeline, called Line 6B. Even then it will likely run at reduced rates.

The Environmental Protection Agency had enforcement officials at the excavation as they investigate whether Enbridge was negligent in the period leading up to the July 26 spill, EPA administrator Susan Hedman said.

The pipeline serves refineries in Michigan, Ohio, Pennsylvania and Ontario that produce more than 700,000 barrels a day. At least three plants have cut output and others have been forced to seek supplies on alternate pipelines.

The spill represents one of the largest pipeline leaks in recent U.S. history. It arguably gained increased profile against the backdrop of the much bigger BP disaster in the Gulf of Mexico.