An explosion ripped through Mexico's second-largest oil refinery Saturday, causing a massive fire and killing two workers, though production was not affected, state oil monopoly Pemex said. The explosion occurred at the 315,000 barrel-per-day Tula refinery in central Mexico while the company was running a trial of a visbreaker, a unit used to reduce viscosity when distilling crude oil, a Pemex spokesman said. The visbreaker, one of several at the refinery, recently underwent maintenance work and Pemex workers were testing it on Saturday to restart the unit, the spokesman said. When a visbreaker fails, refineries end up with excessive fuel oil inventories that could hamper operations. One worker was taken to hospital with serious injuries caused by the blaze, which was brought under control within an hour, Pemex said in a statement. “The accident occurred in a small, very localized area, and so the refining production process was not affected,” the statement said. “Operations are continuing normally.” Pemex said it is investigating the cause of the accident. The number of injured could be higher and a helicopter was being used to airlift workers needing medical attention, said Miguel Garcia, emergency services director for Hidalgo state. Pemex employees were evacuated from the refinery but the fire posed no risk to the surrounding area, Garcia said. Clouds of black smoke were seen billowing out of the refinery in pictures taken by residents near the blast and posted on the social networking site Twitter.
