The death toll from a Mexican gas plant explosion and fire rose to 29 on Wednesday while three workers were still missing one day after the accident, the state-run Pemex energy firm said.

"The number of dead in the accident... has regrettably risen to 29," Pemex said in a statement.

The company had reported late Tuesday that 26 people had died in the inferno at a Pemex gas distribution center near Reynosa, a city on the US border.

But another worker succumbed to his injuries on Wednesday, while two others who were reported missing turned up dead, a company spokeswoman told AFP.

The company revised the number of people injured to 26 and those missing to three, after previously reporting that 28 were injured and seven were missing.