MEXICO CITY — Mexico's state-owned electrical power company acknowledged Tuesday it presented a falsified brush fire report to explain a widespread blackout in December.

The Federal Electricity Commission has been criticized for being antiquated and polluting, and it has hotly denied the outage was the result of incompetence. Instead, it said, the fire caused a kind of huge short-circuit that spread.

The Dec. 28 problem in the state-owned power company's transmission lines caused a two-hour blackout that affected one-fourth of the country's customers.

The company published a supposed report of a brush fire in an area beneath power pylons that it claimed caused the blackout. But the northern state of Tamaulipas maintained that the document, purportedly issued by a state civil defense office, was forged.

On Tuesday, Noe Peña Silva, the utility's director of transmission, said the case against the employees who submitted the purportedly falsified document had been referred to the commission's internal affairs office.

"The reactions around this falsified document should be investigated," the commission's director, Manuel Bartlett, said. "Of course people will bear responsibilities for circulating this falsified document."

"But on the other hand, this situation is being used to distract attention from what is really important, the correct functioning of the nation's electrical system," he said.

The state-owned utility has been criticized as a bastion of old-style, centralized government, because it has resisted the growth of renewable energy and sought preferences for its old, fuel oil-fired power plants.

President Andrés Manuel López Obrador has hotly defended the commission, as he does every state-owned industry, and also stood by Bartlett, an old-guard politician who served in some of the most anti-democratic administrations of the old ruling Institutional Revolutionary Party.

Both López Obrador and Bartlett claim private power generation companies have been given preferential terms in selling power into the grid, but create problems by generating intermittently and not contributing enough to upgrade transmission lines.

The falsification scandal cuts to the heart of López Obrador's central pledge — "Not to lie, not to steal, not to betray the people."