(Updates death toll)
MEXICO CITY Aug 8 (Reuters) - Two workers died after being overcome by a burst of flames in an accident that also injured 11 at a refinery in northern Mexico, state-run oil company Pemex said on Friday.
The accident took place at a fuel barrel storage area in the Ciudad Madero refinery just outside the port city of Tampico in Tamaulipas state while the facility's coking plant was undergoing maintenance, the company said in a post on its Twitter feed.
Pemex said on Friday afternoon via Twitter that one person had been killed. In a separate tweet about six hours later it said a second worker had died in the accident.
Televised images of the refinery showed smoke billowing out of one of the refinery's towers, but Pemex said in a statement that the accident did not cause a fire.
The refinery's installations were not damaged, the company added.
Last month, a fire at one of the refinery's fuel storage tanks forced the facility to shut down until about 90,000 barrels of gasoline were consumed.
The Ciudad Madero refinery, the smallest of Pemex's six domestic refineries, can process up to 190,000 barrels of crude oil per day. (Reporting by David Alire Garcia and Christine Murray; Editing by Jonathan Oatis and Robert Birsel)