A week after a tide of toxic naphtha fuel spewed out of a ruptured pipeline and down the Aguadulcita River, killing any wildlife it touched, locals are fed up with Mexico's failure to patch the rusting pipes beneath them that carry the oil and oil products that are the economy's lifeblood.

"They've banned us from going out on the river because of contamination. It could be another two months," said Carlos Isidro, 34, one of hundreds of stranded fishermen in El Muelle, near the Gulf of Mexico port of Coatzacoalcos.

"We have families to feed. What are we supposed to live on?"

The naphtha leak was the fourth spill at state energy monopoly Pemex in as many months, capping decades of environmental damage in the Gulf of Mexico states where the oil industry is centred.

The spills are one more embarrassment for President Vicente Fox's government, which was supposed to symbolise progress but has failed to gain the upper hand against violent criminal gangs, corruption and reform-wary opposition lawmakers.

While locals know their economy depends on the oil and petrochemical plants that dot Veracruz state's lush tropical forests, they are afraid accidents will multiply with half of Pemex's pipelines now 30 years old and badly corroded.

"There are worse things than oil in those pipes. Imagine an ammonia spill, it would kill us in an instant," said fisherman Nicolas Magana, as masked Pemex workers sprinkled lime to disinfect the remnants of heaps of dead fish in El Muelle.

"We are living in a time bomb," muttered a woman onlooker.

ACRID FUMES, BLOATED COWS

Pemex, shamed by photos of dozens of bloated dead cows and heaps of dead fish, has cleaned up the worst of the spills, buried the cows and trucked drinking water to Agua Dulce.

Visiting the area, Pemex chief Luis Ramirez blamed the decrepit pipelines on under funding. Pemex, which pays taxes worth 61 percent of its revenue, complains its hands are tied because Congress controls its operating budget.

The company estimates it needs an extra $9 billion over three years to repair 22,961 miles (36,950 km) of pipelines.

Congress, however, likes to channel oil profits into politically popular areas like healthcare and education. Pemex has focused its spending on exploration, amid concern that output from its main oil field will start declining next year.

"People here live in constant fear of a spill. But they know Pemex has not had the resources to carry out maintenance," said Agua Dulce town hall official Juan Enrique Ibarra.

Yet locals in Agua Dulce, many living on a pittance in crude concrete and corrugated iron homes, had less sympathy for Mexico's biggest company after acrid fumes wafted into their yards, scaring them and causing nausea and headaches.

Hundreds of families were temporarily evacuated from the town, whose name means fresh water.

Some 20 miles (32 km) away, the tiny town of Nanchital is still suffering the after-effects of a December oil spill that flowed down the Coatzacoalcos River onto beaches, coating seabirds and killing river life.

Black gunk stains trees and rocks along the river's edge, and an oily film coats the surface. Onshore, sand beneath the surface is black and stinks. Fishermen say the fish have fled.

"The fish smelled the oil and left," said Guillermo, who after paddling his wooden skiff for 12 hours had caught only 50 pesos ($4.50) worth of fish to support his family of 10.

TOXIC CHEMICALS

Locals in Coatzacoalcos, who have cohabited with Pemex since the 1940s, have lived through frequent spills and are resigned to contamination.