Mexican state-owned oil monopoly Pemex said its crude shipments were back to normal after bad weather shut its main Gulf of Mexico exporting ports this week and killed 19 oil workers in a rig accident.

Mexico's oil ports were all open on Friday and ships were leaving as normal. A Pemex spokesperson said the fact some shipments were delayed by a few days would not affect Mexico's monthly oil export levels.

''Everything is now functioning again,'' the spokesperson said. ''We expect to meet the export program established for the month.''

The Gulf of Mexico oil ports of Dos Bocas, Cayo Arcas and Coatzacoalcos were shut on Tuesday as a cold front whipped up waves and high winds, but reopened by Thursday afternoon.

The stormy weather caused an offshore oil platform to keel over and collide with an adjacent rig, setting off leaks of oil and natural gas.

At least 19 out of 86 oil workers who jumped into life rafts in churning seas died as one raft broke up and rescuers took hours to reach them. Navy rescue teams continued on Friday to search the sea and nearby beaches for four more missing oil workers.

Mexican media voiced concern about the quality of the life rafts, one of which was smashed apart by the waves and washed up on a beach. Survivors recovering in hospital said some of the rig workers could not swim.

Mexico is a top three oil supplier to the United States, which takes around 80 percent of its neighbor's oil exports.