A U.S. government agency is investigating an oil leak of about 1,200 barrels (190,000 litres) that seeped out of an Enbridge pipeline in Wisconsin, which was delivering Canadian crude to Chicago-area refineries.

On Saturday, the U.S. Transportation Department's Pipeline and Hazardous Materials Safety Administration said that it was investigating the cause of the pipeline failure and that an inspector has been sent to the locale.

The Alberta-based company is busy cleaning up the leak and has shut down part of that pipeline.

"Enbridge is treating this situation as a top priority. We are bringing all necessary resources to bear," a company official said in a statement after Friday's spill, which forced the closure of Line 14 running through Grand Marsh in central Wisconsin.

"Our immediate focus is on keeping our workers and the public safe as we work to remove the oil and clean up the site," said Richard Adams, vice president of U.S. operations at Enbridge.

It's not known how long the line, which is part of the Lakehead route, will remain closed. The cause of the spill has yet to be determined.

The company announced late Friday it had contained the spill to a field that is part of the pipeline right-of-way. The incident is a new blow to the Calgary-based firm, which is still facing criticism for a spill that fouled Michigan wetlands two years ago.

About three million litres of heavy crude spilled from a ruptured Enbridge pipeline into the Kalamazoo River in 2010. Investigators with the U.S. Transportation Safety Board released their findings earlier this month and ripped into the company, noting it did nothing for 17 hours after oil started gushing and that it knew about small cracks in the pipeline for five years.

Enbridge is also seeking to build an oil pipeline across northern British Columbia. The Northern Gateway project would bring bitumen from the Alberta oilsands through B.C. to Kitimat.

Friday's incident isn't the only oil pipeline leak involving an Alberta-based firm this summer. As much as 475,000 litres of light sour crude escaped last month from a Plains Midstream Canada pipeline into a man-made reservoir, Gleniffer Lake, via the Red Deer River in Alberta.

Officials say the cleanup from the rupture near Sundre, Alta., will take months, possibly even to the end of the summer.

With files from The Canadian Press