Air and sea search teams intensified their hunt Saturday for 10 missing oil workers as tropical storm Nate headed west, threatening new areas of Mexico's gulf coast where hurricane conditions are expected.

In another development, fishermen groups reported at least a dozen of their colleagues aboard two Mexican shrimp boats have been missing in the gulf since Friday.

Nate was still moving toward the coast very slowly, but was expected to pick up speed Saturday, the U.S. National Hurricane Center in Miami. Forecasters said the storm would reach the coast Sunday, mostly likely with near hurricane intensity.

Helicopters from the Mexican navy and the state oil company, Petroleos Mexicanos, left ports along the coast of Tabasco state to scour the sea, while other crews searched the beaches closest to the spot where the 10 abandoned their disabled liftboat for an enclosed life raft in the storm about midday Thursday.

"The hope is that we find them alive at sea," said one navy rescuer searching the beach at Frontera on the Tabasco coast. He didn't give his name because he wasn't authorized to speak to the news media.

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In this NASA satellite image made on Friday, tropical storm Nate is seen approaching the Mexican coast. ((NASA/Associated Press))

By Saturday afternoon, authorities said they still had found no sign of the workers. The employees of Houston-based Geokinetics Inc. called for help Thursday afternoon after leaving the vessel Trinity II.  The missing include four U.S. workers, four Mexican workers, one worker from Kazakhstan and a 10th of unconfirmed nationality.

Mexico's National Water Commission reported that the rain had diminished significantly in the Bay of Campeche where the workers disappeared as Nate raged more than 200 kilometres away from the area, threatening the coast of Veracruz state.

A liftboat can lower legs to the sea floor and then elevate itself above the water level. This one was being used as a recording vessel and housing for the crew, and it was in about eight metres of water.

Randy Reed, president of the vessel's owner, Trinity Liftboat Services LLC in New Iberia, La., was not available for comment Saturday, according to a woman who answered the phone there. The Mexican navy said Friday night that sailors had reached the 29-metre Trinity II but found no crew.

Geokinetics spokeswoman Brenda Taquino said the life raft was a sealed capsule containing enough food and water to last for several  days, but there was no way to communicate with it.

Elsewhere, fishermen associations of Campeche reported that two shrimp boats have been missing since Friday along with at least a dozen people. They were in the gulf heading to the state of Tamaulipas when they were surprised by the tropical storm.

Weather forecasters say Tropical Storm Nate is growing stronger and could be near hurricane strength when it hits Mexico on Sunday.

Growing in strength

The U.S. National Weather Service said at 4 p.m. ET Saturday that Nate was centred 195 kilometres east-northeast of Veracruz, with maximum sustained winds increasing to 100 km/h. It was inching westward and winds will strengthen in the next 24 hours, the service said.

A hurricane warning was posted along the coast from Tuxpan to Veracruz and a hurricane watch from south of Veracruz to Punta El Lagarto. The service said the government should act to protect life and property.

Pemex said it had evacuated 473 workers from platforms off the coasts of the gulf coast states of Veracruz and Tamaulipas. Mexico's gulf ports were closed to navigation. Veracruz state officials also ordered schools closed Monday as a precaution.

In the far North Atlantic, what's left of Hurricane Katia is weakening but is still expected to bring strong winds to the British Isles on Monday, the U.S. National Weather Service said. The storm was centred about 475 kilometres east-southeast of Cape Race, N.L.

In the Caribbean, the remnants of Maria are barely a tropical cyclone. Forecasters said Maria was about 500 kilometres east-southeast of San Juan, Puerto Rico, with winds reaching 64 km/h.