Interline Resources Corp. is continuing to reduce debt, this time with the sale of its Monument Butte gas pipeline system to Questar Gas Management Co. for $4 million. It is the largest asset Interline has sold to reduce its debt.

The company, which owns the technology to refine used oil, expects a gain of about $2 million from the sale, which will be reflected in its second quarter ending June 30, a spokesman said.Interline is selling off assets to reduce $7.2 million in debt, all of which is in default. In addition to the pipeline sale, Interline has also sold its 40 percent interest in a refinery in England to businessman Jon Whelan and the marketing rights for South Korea, Japan and China to Dukeun Industrial Co. of Seoul, South Korea, raising a total of about $900,000.

The Monument Butte natural gas line consists of 28 miles of main trunk line and 40 miles of lateral lines connecting 146 wells and five compressors. The sale includes 12 producing oil wells in that area.