U.S. investigates acid leak at refinery CORPUS CHRISTI, Texas, March 10 (UPI) -- A federal agency has begun an investigation into a Citgo Petroleum Corp. refinery in Corpus Christi, Texas, after sensors detected a leak of hydrofluoric acid. A team from the Chemical Safety Board began work at the refinery Wednesday, ABC News reported. They arrived two days after emergency containment measures automatically went into place at the alkylation unit. A fire and explosion in the alkylation unit in 2009 severely injured one employee. A report last year said 4,000 pounds of hydrofluoric acid were released, more than 100 times Citgo's original estimate of 30 pounds. Chemical Safety Board Chairman Rafael Moure-Eraso said the current investigation was undertaken "because of the toxic nature of hydrofluoric acid and the need to keep it contained, or to mitigate the consequences of a release." Citgo said in a statement that people living around the plant were never in danger from this week's incident.