An oil spill has spread more than 50 kilometers (30 miles) along a river in the Mexican state of Veracruz despite assurances by the state oil monopoly that the leak has been repaired, local officials said Tuesday.

Civil protection officials in the town of Tierra Blanca said the Arroyo Hondo river had turned red from the oil and wildlife was turning up dead along its path.

Salvador Cruz, the municipality's civil protection chief, told AFP he had inspected the area and found "dead rabbits, field mice, fish, chicken, eels, turtles and river cranes."

Cruz warned that the oil was nearing a lake downstream, the Maria Lizamba, threatening the livelihoods of people who live from fishing there.

Pemex, the state oil company, said Monday night the leak was caused by oil thieves breaking into a pipeline.

It said it has been working to contain it since it was first discovered August 28, and has repaired the leak and recovered 250,000 liters of oil and water.

However, it put the affected area at 1,200 meters (yards).

It was the latest in a series of serious environmental mishaps in Mexico.

Two weeks ago a pipeline leak blamed on oil thieves polluted the San Juan River, which waters farm lands in the northern state of Nuevo Leon.

Just days earlier, 40,000 cubic meters from a copper mine were dumped into the Sonora river in northwest Mexico, an event government officials described as "the worst environmental disaster" in the mining industry in recent years.