Mexico’s national oil company Pemex said on Friday it may be forced to shut its largest refinery in the next few days if ongoing protests in the southern state of Oaxaca continue to block local roads needed to transport fuels.

“If the blockades continue, it will be necessary to shut down the operations of plants at Salina Cruz in the next few days,” the company said in a statement, referring to the refinery which has daily crude processing capacity of 330,000 barrels.

A dissident teachers union has escalated protests in Oaxaca state, home to the Salina Cruz refinery, including road blockades following the arrest of its leader for alleged corruption last weekend.