( CNN ) -- An explosion rocked the Amuay oil refinery in northwestern Venezuela , killing 39 people , including a 10-year-old boy , a Venezuelan official said Saturday . More than 80 people were injured , Vice President Elias Jaua told state-run VTV . `` People are very scared , '' said Falcon State Gov . Stella Lugo , according to the state-run AVN news agency . `` They evacuated the areas that had to be evacuated , but the situation , as the technicians are telling within the refinery , is controlled . '' President Hugo Chavez decreed three days of mourning and gave his condolences to families of the victims . The incident occurred at 1:11 a.m. when `` we had a release of gas whose origin we are going to determine , '' Rafael Ramirez , president of the state-owned petroleum company PDVSA , told VTV . `` The gas generated a cloud that then exploded and provoked fires in at least two tanks of the refinery and in the surrounding areas . '' He said the explosion damaged the infrastructure of the refinery and nearby houses . The refinery -- one of the world 's largest -- is part of the giant Paraguana complex in Falcon state . Venezuela , a founding member of the Organization of the Petroleum Exporting Countries , is one of the world 's largest oil exporters . The nation has a refinery capacity of more than 1 million barrels per day , according to OPEC . Venezuela 's oil revenues represent some 94 % of the country 's export earnings , more than half of federal budget revenues and some 30 % of gross domestic product , OPEC says . The South American country sends a large percentage of its exports to the United States , according to the U.S. Energy Information Administration . CNN 's Pierre Meilhan and Nelson Quinones contributed to this report .
Chavez declares three days of mourning . Blast damages refinery buildings and nearby houses . More than 80 people are injured .