– The Federal Railroad Administration on Friday ordered rail tank car owners to replace defective valves never approved for installation on thousands of tank cars, causing oil to spill from moving trains.

The directive applies to a 3-inch valve installed on roughly 6,000 tank cars, and their owners have 60 days to replace them. Within 90 days, tank car owners must also replace 37,000 1-inch and 2-inch valves manufactured by the same company. While the smaller valves were not found to be defective like the larger ones, they were not approved for the tank cars.

The affected cars can be used in the interim, but none can be loaded with hazardous materials if they are still equipped with those valves after the deadlines.

Railroads don't own most of the tank cars used to transport oil.

The enforcement action comes after a story last month in the Bellingham (Wash.) Herald about 14 tank cars that were discovered leaking en route from North Dakota's Bakken region to the Tesoro refinery in Anacortes, Wash.

The agency said it had sanctioned the operator of a North Dakota loading facility for not properly closing a valve on another oil car after the car arrived at the BP Cherry Point refinery in northwest Washington state with 1,600 gallons missing.

That spill was discovered in early November but wasn't reported to state officials until early December. Local emergency officials were never notified, according to a report sent by BNSF Railway to the U.S. Department of Transportation and the Washington state Utilities and Transportation Commission.

The 1-inch, 2-inch and 3-inch valves were all manufactured and sold by McKenzie Valve and Machining, a company in Tennessee. The company did not immediately respond to messages.

The Federal Railroad Administration also announced Friday that it was launching a full audit of the approval process for tank car components to determine why the unapproved valves were installed.

Under federal regulations, tank car valve designs must be approved by the Association of American Railroads Tank Car Committee.

The Federal Railroad Administration said it would begin working immediately with the association, which is the rail industry's principal trade group in the nation's capital.

Sarah Feinberg, the FRA's acting chief, said Friday that removal of the valves will help reduce the number of non-derailment releases of hazardous materials.

"Any type of hazardous materials release, no matter how small, is completely unacceptable," she said in a statement.

Ed Greenberg, a spokesman for the railroad association, said Friday that it supported the order. "Officials from our association will be working closely with the administration in reviewing the tank car valve approval process to ensure the agency is fully satisfied with the current approval requirements that are in place," he said.