DURANGO, Colo. (AP) — Investigation agencies in Colorado have not determined what ignited a well site explosion last year that killed a worker.

Randy Yellowman, 47, was working as a contracted truck driver when his body was found by ranchers after a storage tank exploded at the natural gas well pad near Durango in January 2019, The Durango Herald reported Tuesday.

The U.S. Department of Labor's Occupational Safety and Health Administration fined his employer, Overright Trucking Inc., more than $10,000 this summer for safety violations and procedural failings that the agency said likely led to...