What caused the Red Butte Creek oil spill and how Chevron plans to deal with it are some of the questions U.S. Rep. Jim Matheson raised Wednesday in a pair of letters to key federal agencies.

The 2nd District Democrat sent one letter to Transportation Secretary Ray LaHood urging a thorough and speedy probe into how a pipeline carrying crude oil was able to break and leak, undetected, for hours over the weekend. He also prodded LaHood to disclose the findings to the public and determine what can be done to prevent another spill.

In a second letter, to U.S. Environmental Protection Agency Administrator Lisa Jackson, he focused on the cleanup ahead.

"The spill and subsequent environmental consequences is of grave concern to me and my constituents," Matheson wrote. "My top goal is ensuring that this spill is fully cleaned up and all traces of oil removed.

"... I look forward to continuing to work with you," Matheson concluded, "to ensure that Chevron lives up to its duties to mitigate the environmental consequences resulting from the spill and returns the waterways, wildlife and surrounding land to their natural state."

About 33,000 gallons of medium crude leaked from the pipeline, ran down Red Butte Creek and into the Jordan River. While local, state and federal officials say the spill has been stopped and contained, crews are expected to be cleaning up oil from the streambeds and shorelines for weeks or maybe months. Chevron has removed about 21,000 gallons of oil, largely from Liberty Park's pond.