A worker at Mexico's Cadereyta oil refinery was killed in an explosion, state oil monopoly Pemex confirmed on Tuesday.
Pemex said in a press release that the accident occurred following a leak in a compressor at the gasoil hydrotreater unit at the refinery that resulted in a brief fire.
Pemex did not provide an update on the operational status of the refinery in the press release.
Local media in northern Mexico initially reported that seven people had died in the explosion at Pemex's Cadeyreta complex.
The oil refinery is Mexico's most sophisticated and the country's third largest, with a capacity of 275,000 barrels per day. The blast could force Mexico, which already relies on imports for more than 40 percent of domestic gasoline demand, to significantly boost fuel imports.
"We felt the windows shake. It was only a few seconds, but the whole building shook," said Jose Luis Garza, a government employee in Juarez, about 20 minutes from the refinery.
U.S. crude oil and RBOB gasoline futures pared losses slightly after the explosion.
Mexico bought 432,000 barrels a day of fuel from the United States in June, making it the top importer of U.S. refined products, according to the U.S. government.
"Mexico is already short of refining capacity and this will make it even shorter," said Antoine Halff, deputy head of research at Newedge Group in New York. "It could well raise oil product prices as Mexico needs to increase imports."
The blast comes in a year marred by serious accidents in the North American oil industry, including the months-long Deepwater Horizon spill, a major pipeline accident in Michigan and an explosion at a Gulf of Mexico natural gas platform.
Guillermo de Leon, head of civil protection forces in Cadeyreta said five people had been seriously injured in Tuesday's explosion.
Francisco Montano, a Pemex spokesman in Mexico City, said the blast took place in one of the Cadeyreta refinery's hydrotreating units, which removes sulfur from fuels under high pressure in the presence of explosive hydrogen gas.
Mexico, the world's seventh largest oil producer, must import fuel due to a lack of refining capacity.
A Gulf Coast products trader said it was "hard to gauge" whether Pemex would pull more U.S. exports in the aftermath of the explosion. "Pemex already moves a lot of cargoes off the Gulf Coast," the trader said.
Pemex, struggling under a mountain of debt and rapidly aging oil fields, is studying a plan to import crude oil for the first time in over three decades to improve the profitability of its refineries.