MEXICO CITY — Mexican officials said Monday they have found a new distribution point for thousands of gallons of gasoline stolen from state-owned pipelines: a seemingly normal gas station with official logos.

Thieves in Mexico had long been thought to unload stolen oil products on shadowy black markets. But it now appears the thefts have taken on a new sophistication, using a gas station that until 2010 had a concession from the state-owned Petroleos Mexicanos company, known as Pemex, to legally sell gas.

A Pemex official who was not authorized to be quoted by name said Monday that it was the first time that stolen fuel has been detected being sold through a gas station. In the past, primitive illicit fueling stations with improvised tanks had been discovered in fields, vacant lots and industrial buildings, presumably to supply fuel to private fleets.

But in a raid over the weekend in the northern city of Monterrey, the federal Attorney General's Office said it found about 12,690 gallons (48,000 liters) of stolen gasoline at the station, worth about $77,000. The station came under suspicion because it had not had a legitimate delivery of gas in some time.

Photos of the station showed that it had the normal green, red and white signs borne by all Pemex gas stations throughout Mexico. Pemex licenses the stations to be run by private concessionaires, who must buy fuel from the company. The Attorney General's Office said the Monterrey station's concession had been canceled in 2010.

The company is taking the threat seriously enough that it is starting a nationwide, random audit of stations throughout the country, in part because the volume of oil products being stolen appears to be too large to move through primitive, improvised outlets.

The company says it lost about 2.99 million barrels, or about 125 million gallons, of oil products in the first 11 months of 2011, the latest figures available. That represented about a full day's worth of total production for the company, and marked a 52-percent increase over the 1.96 million barrels stolen in the same period of 2010.

According to a U.S. court case, Mexican gangs trafficked some stolen crude over the border to U.S. refineries, and in June 2011, Pemex filed a lawsuit against nine U.S. companies and two individuals for alleged involvement in buying or processing Mexican oil products stolen by gangs.

Thieves have also sold unrefined fuels to bulk users such as brick kilns and factories, but the amount of gasoline being stolen would be inappropriate for such uses, or even private truck fleets.

Pemex said the task force will use mobile labs to test stations' gasoline to detect whether it was illicitly mixed or transported. It will also review tax and commercial records to detect whether any station is selling more gas than it has ordered.

But the 1,324 illegal taps and break-ins at Pemex pipelines discovered in 2011 are only part of the complex series of attacks on the company.

A Mexican legislator said Monday that an oil spill in early January in the Gulf coast state of Veracruz was intentionally caused to create a pollution emergency, in order to generate income and contracts for clean-up work.

Federal Congressman Antonio Benitez Lucho toured the Pemex plant where the spill originated and said a primitive cut had been made in a valve head, a hole knocked in a containment wall and a thick hose laid to the edge of the Coatzacoalcos river, which empties into the Gulf of Mexico.

In early January, about 63,400 gallons (240,000 liters) of crude spilled from the valve plant, blackening the river's shores and threatening wildlife.

"There was no doubt that it was deliberate," Benitez Lucho said.

"I think they spilled the crude so that the companies that do clean-up and remediation work ... could get quick, fast-track contracts," he said. "They are million-dollar companies that charge huge amounts for clean-up and remediation, and I think that is the motive."

The office of the Federal Attorney General for Environmental Protection said the case was still under investigation.