CALGARY, Alberta- Enbridge Inc shut down its Line 5 oil pipeline for several hours on Tuesday after protesters trespassed onto a facility in Michigan and tampered with the pipeline, an Enbridge spokesman said on Wednesday.

Line 5 ships around 540,000 barrels per day of crude from Superior, Wisconsin, to Sarnia, Ontario. Spokesman Ryan Duffy said the line was back up and running and Enbridge did not anticipate any impact on deliveries to customers.

Environmental campaigners said a protester turned a safety valve on the pipeline.

"The water protector called Enbridge so that they could safely halt the flow of oil before reading a statement and turning the valve to halt the operation of the pipeline," said an emailed statement from the Resist Line 3 Media Collective, which is also opposed to Enbridge's Line 3 pipeline.

Line 5 is at the centre of a dispute between Calgary-based Enbridge and the state of Michigan, which in May sought to halt operation of the pipeline over concerns a section running underwater in the Straits of Mackinac could leak. Enbridge ignored Michigan's order.

Duffy said Enbridge would seek the prosecution of all those involved in Tuesday's protest.

"The actions taken to unlawfully trespass on our facility in Michigan and attempt to tamper with energy infrastructure was reckless and dangerous," Duffy said.

(Reporting by Nia Williams; Editing by Andrea Ricci) ((nia.williams@thomsonreuters.com; +1 403 531 1624; Reuters Messaging: nia.williams.thomsonreuters.com@reuters.net))