ASHLAND, Ky. — A man killed in an explosion at the AK Steel Coke Plant last week opened an access panel to a high pressure gas line that triggered the explosion and fire, investigators from the Kentucky Fire Marshal’s office said Tuesday.

Fire Marshal William Swope said the investigation showed that Forest Brent Finley, 61, of Milton,, W.Va., employed by Dixon Electrical Systems of Huntington, W.Va., was to have been working on a nearby electric panel instead.

Firefighters from the Ashland Fire Department were able to recover Finley’s body less than an hour after the noon explosion, after plant workers had turned off gas lines to the area and allowed the fire to burn itself out.

No other injuries were reported. Fire Chief Scott Penick said firefighters kept the incident from becoming worse by keeping tanks and lines in the area hosed down.

The company did not say when the plant will be restarted.

The 93-year-old plant is scheduled to be shut down permanently this quarter anyway. About 260 workers will lose their jobs.

The plant produces coke to fuel the blast furnace at AK’s Ashland steel mill four miles away. The decision to close it was announced by the company earlier this year. It said in a press release earlier this year that the plant is “no longer cost-competitive due to increased maintenance and increasingly stringent environmental regulations.”