A blaze at Venezuela\'s main oil refinery, which has left 48 people dead, spread on Monday to a third fuel storage tank, Energy and Oil Minister Rafael Ramirez said, insisting it was under control. \"We must announce that a third tank... is on fire,\" said Ramirez, who is also the head of state oil firm Petroleos de Venezuela (PDVSA), which operates the Amuay refinery in Falcon state. Ramirez insisted that firefighters were working to \"control and confine\" the blaze, which first erupted on Saturday after a suspected gas leak. The fire had previously been confined to two of nine storage tanks that were set ablaze at the refinery. On Monday, the flames and a massive plume of smoke were still visible several kilometers (miles) away from the refinery. More than 220 firefighters were still at the scene, the government said. The accident is the worst ever for PDVSA. About half of the dead were members of the National Guard tasked with surveillance at the site, according to Falcon State governor Stella Lugo. President Hugo Chavez, who declared three days of national mourning, has ordered the opening of an investigation into the incident.