DENVER - BP and Halliburton have both been fined for the fatal explosion at a natural gas compression station in southwestern Colorado.

A worker was killed in June's explosion 15 miles east of Durango. Halliburton and other contractors were doing maintenance work on a BP pipeline at the time.

Colorado Public Radio reported Thursday that federal regulators found that a valve on the pipeline was left closed. That caused pressure to build up quickly, rupturing the pipeline.

According to the Durango Herald, Mancos resident Randy Mathews, 42, was killed in the explosion. The blast also injured two other workers.

An Occupational Safety and Health Administration citation obtained by the station faults BP and the contractors for not having safety procedures in place before the work began. BP, Halliburton and the other contractors were each fined $7,000 -- the maximum allowed under the law.