A deadly incident on a drilling platform in the Gulf of Mexico was related to routine maintenance and not production, Fieldwood Energy said.

The Bureau of Safety and Environmental Enforcement was notified by Fieldwood of an explosion on its Echo Platform. One contract worker was killed and three others were treated for injuries at an onshore medical facility.

Fieldwood said a contract worker with Turnkey Cleaning Services was cleaning what's called a heater treater, a piece of equipment used to separate oil from water, at the time of the deadly incident.

"It was an isolated pressure event that occurred inside the heater treater and did not result in a fire on the platform," the company said in a statement late Friday. "This incident was not related to a drilling operation but, instead, occurred during maintenance operations at the platform."

The platform was idle for about a week for routine maintenance operations at the time of the accident. No oil was spilled, and no secondary pollution was reported during the incident.

"We do not have additional details at this point," the company said. "We are working hand in hand with the BSEE, the Coast Guard, and Turnkey Cleaning Services to investigate this incident fully."

The incident was among the first in 2014 in the Gulf of Mexico.

Fieldwood in January acquired the Gulf of Mexico operations owned by SandRidge Energy for $750 million in cash.

The company said the Gulf of Mexico assets hold proved reserves of 57.2 million barrels of oil equivalent, of which 51 percent is oil.