MEXICO CITY (Reuters) - Mexico’s government unveiled a plan on Thursday to step up use of the armed forces to combat fuel theft, vowing to root out corrupt officials it says are largely responsible for a problem that has cost the country billions of dollars.

FILE PHOTO: A policeman inspects barrels containing stolen diesel fuel, stored in a tire repair shop, during an operation in the municipality of Apodaca, neighboring Monterrey July 4, 2011. REUTERS/Josue Gonzalez/File Photo

President Andres Manuel Lopez Obrador told a regular news conference his government would fight the theft “outside and inside” state oil firm Petroleos Mexicanos (Pemex), saying authorities were complicit in the bulk of the crimes.

“This is the theft of national assets, of public funds, of money that belongs to all Mexicans,” he said.

Guanajuato state governor Diego Sinhue said later on Thursday government officials told him the armed forces were “intervening” at Pemex installations around Mexico.

That included facilities in Guanajuato, where Pemex runs a refinery in the city of Salamanca. Fuel theft there has been linked to a surge in violence and killings, he said in a video published by Mexican media.

The operations were conducted in accordance with Lopez Obrador’s order to put an end to fuel theft, Sinhue said.

Criminal gangs have for years used fuel theft as a way to supplement their income, hurting Mexico’s refineries and bleeding money from state coffers.

Speaking alongside the president, Defense Minister Luis Cresencio Sandoval said the security presence would be increased at key oil installations to better monitor distribution of fuel.

Security forces would also receive additional training for the task, Sandoval said.

Pemex’s new Chief Executive Officer Octavio Romero told the news conference more than 146 billion pesos ($7.40 billion) worth of fuel had been stolen in Mexico since 2016, with theft soaring to new heights this year.

Asked whether the Pemex workers’ union had been involved in the theft of fuel, Lopez Obrador said there had been reports that the union had been restricting access to parts of the company’s operations.

That issue had been addressed with the union’s leaders and access would not be restricted in future, he said.