* Echo Platform was not in production at the time of incident
* Fieldwood says offshore facility undamaged
* At least one injured, no pollution was reported (Adds background, byline, company response, recasts lead)
By Ian Simpson
WASHINGTON, Nov 20 (Reuters) - An explosion at oil and gas operator Fieldwood Energy's Echo Platform in the Gulf of Mexico on Thursday killed one person and injured at least one, but no pollution was reported, a U.S. safety agency and the company said.
The explosion occurred just before 3 p.m. CST (2 p.m. EST/1900 GMT) at West Delta 105, about 12 miles (19 km) off the coast of New Orleans, the U.S. Bureau of Safety and Environmental Enforcement said in a statement.
"The Echo Platform was not in production at the time of the incident. The facility damage was limited to the explosion area and there was no pollution reported," it said.
The agency said three people were injured and were being treated at an onshore medical facility.
In a statement, Fieldwood said one employee of a contractor was killed and a second contractor employee was seriously injured. There was no explanation for the discrepancy in the number of injured.
Fieldwood said the platform was undamaged and that it had few details about the accident.
"This was an isolated incident that has been fully contained," it said.
The U.S. safety agency said it was coordinating with the Coast Guard on the response and would investigate the incident.
Fieldwood has become the largest player in the shallower continental shelf region of the U.S. Gulf. The Houston-based company is owned by private equity firm Riverstone Holdings LLC.
Fieldwood bought Apache Corp's Gulf shelf assets for $3.75 billion in July 2013. It acquired SandRidge Energy Inc's Gulf assets for $750 million in January. (Editing by Himani Sarkar)