Environmental watchdog Profepa, whose inspectors visited the spill site on Wednesday, estimated 5,000 liters (1,300 gallons) of crude oil spilled out from the pipeline, which it said was corroded.

Pemex reported a smaller spill, also in Veracruz state, on Monday, when oil and diesel fuel seeped into the Chiquito river from a faulty pipeline.

Fishermen and farmers in Veracruz and neighboring states Tabasco and Campeche have suffered from soil and water contamination for years, the price they pay for living among Pemex's myriad oil and petrochemicals installations.

Environmental groups last month lodged a legal complaint against Pemex over a major crude oil spill in December, also in Veracruz state, that coated the banks of the Coatzacoalcos river and drove away fish.

State-controlled Pemex has reported more than half a dozen spills of oil or oil products since last October, including a spill of toxic naphtha fuel in another part of Veracruz state that killed dozens of cows.

The company, which pays 61 percent of its revenues in tax, says it needs 150 billion pesos ($13.4 billion) for urgent repairs to its pipelines, half of which are more than 30 years old and corroded, according to Mexico's IMP oil research institute.