MEXICO CITY (AP) -- Mexico's top prosecutor said Sunday the government planned to order the arrests of "many more" people -- including potentially government officials -- involved in fuel theft networks between Mexico and the United States.

On Saturday, the Mexican government announced the arrest of a senior Mexican navy officer, who is related to the former head of Mexico's navy. He was arrested along with 13 others officials and businesses leader connected with a massive fuel seizure in northern Mexico.

The head of Mexico's prosecutor's office Alejandro Gertz Manero and other officials said the arrest was a sign that the government was cracking down on fuel theft, known in Mexico as huachicol. Critics say it's just a sign of the depth of the problem.

The detention notably comes just days after U.S. Secretary of State Marco Rubio paid a visit to Mexico to discuss security issues, and put pressure on the Mexican government to crack down on fuel theft, which has gradually lined the pockets of Mexican cartels.

Fuel theft is a major problem in the Latin American nation, and has cost the state-owned oil company Pemex $3.8 billion in just five years. The fuel is often illegally tapped and resold in Mexico, or cheaper gasoline or diesel are bought in U.S. border states like Texas and smuggled into Mexico without paying import taxes.

Gertz Manero and Mexico's Security Secretary Omar García Harfuch on Sunday maintained they were "isolated cases" within the Marines and dodged questions about the depth of the fuel theft networks within the government.

Observers have long commented that a great deal of corruption is required for criminal networks to have such success. The detention of 14 people has further confirmed those suspicions, indicating in more detail that illegal networks profiting from fuel theft are fueled by wider levels of corruption in Mexico's government and businesses, said Mexican security analyst David Saucedo.

"Huachicol networks require a level of political, military and police protection," Saucedo said.

Saucedo added that it's only recently, under the pressure of Rubio, that the Mexican government has begun to more aggressively crack down on the theft.

Mexico's Security Secretary Omar García Harfuch defended Mexican security authorities, saying "the actions of a handful of isolated people doesn't mean they're acting in the name of a respectable institution."