(Adds interruption of electric supply to refinery)
MEXICO CITY, June 28 (Reuters) - Mexico's state-owned oil company Pemex said on Tuesday that it has ordered a "preventative shut down" of the catalytic unit at its Salina Cruz refinery due to a power interruption that caused smoke to be detected at the unit.
The electric supply interruption forced the company to shut down the catalytic unit, but other parts of the refinery continue to operate normally, a company spokesperson said.
The catalytic plant is one of the refinery's main production units used to separate crude oil into lighter petroleum products like gasoline.
The Salina Cruz facility, located in southern Oaxaca state, is Pemex's largest domestic refinery with a capacity to process 330,000 barrels of crude per day. (Reporting by David Alire Garcia and Ana Isabel Martinez; Editing by Chizu Nomiyama)