Two workers died and another remained missing after a raging fire broke out early on Friday morning at an offshore platform run by Mexican state oil company Pemex just off the southern edge of the Gulf of Mexico.
In posts on Twitter, Pemex said it had accounted for all other workers and said oil production had taken a major hit from the blaze.
Video circulating on social media showed the massive platform and its tangle of pipelines engulfed in flames as nearby boats sought to douse the fire with hoses.
The platform operates in the company's Cantarell Field, once one of the world's most productive.
Earlier in the day, Pemex said six people had been injured in the fire, which it said started at the Nohoch-A platform and then spread to a compression platform.
It was not immediately clear on Friday evening whether the casualties were among the six injured.
Later on Friday, the company said oil production had been "impacted in a substantial way" due to the fire. Pemex did not offer further details on the impact on output.
"Our technicians are studying how to repair the pipelines, interconnections and other works to restore it," the company said in a separate post on Twitter.
Chief Executive Officer Octavio Romero referred to the impact in a video the company posted.
"We're going to keep looking for this person as our number one priority, as well as think about how we can reactivate activity in the area because Nohoch is very important," he said.
A Pemex statement Friday morning indicated that 321 of 328 people working on the sprawling platform had been successfully evacuated.
Over the past decade, Cantarell has seen its crude output slide significantly. But it is still responsible for around 170,000 barrels per day, according to company data.
The vast majority of Mexican oil production comes from nearby shallow water fields clustered around the Bay of Campeche in the southern Gulf, where Pemex has suffered a number of industrial accidents in recent years.
Reporting by Ana Isabel Martinez; Additional reporting by Stefanie Eschenbacher, Kylie Madry, Manuel Carrillo and Brendan O'Boyle; Editing by Isabel Woodford, David Gregorio and Rosalba O'Brien
(Reuters - Reporting by Brendan O'Boyle; Editing by David Alire Garcia)