The source added that no injuries were reported in the incident.
Television images showed a dense plume of black smoke rising from inside the refinery.
Oaxaca Civil Protection reported on its Twitter account that access to the complex was restricted. “With the support of @PolVial_GobOax and @Policia_GobOax, the zone is being cordoned off to avoid eventualities,” he said.
Salina Cruz, Pemex’s largest refinery, has a capacity to process 330,000 barrels per day of crude, according to data from Eikon Refinitiv. In August, another fire broke out in its facilities.