Federal regulators say a company shut down a Michigan pipeline for planned maintenance hours before 911 calls about odors in the area where a massive oil spill was reported the next day.

National Transportation Safety Board officials told reporters Monday that Enbridge Inc. shut down its Calhoun County oil pipeline about 6 p.m. July 25. About three hours later, calls started coming in about gas odors in the Marshall area.

But NTSB officials say they can't link the shutdown to the pipeline rupture that dumped hundreds of thousands of gallons of oil into a Kalamazoo River tributary. It hasn't found the cause.

Federal officials say a Consumers Energy worker found oil on the ground on the morning of July 26. Enbridge says it detected the leak that day.