JONACAPA, Hidalgo (AP) — Authorities in central Mexico said Tuesday they found the bodies of nine men in vehicles near a fuel pipeline.

The circumstances around the deaths remained under investigation, but there were indications that fuel theft may have been involved. Mexico faces a problem with gangs that steal gasoline, diesel and natural gas from government pipelines.

Ángel Rangel Nieves, police chief of San Juan del Rio city in the central state of Queretaro, said the bodies were found in two vehicles near the pipeline north of Mexico City. The vehicles had license plates from the neighboring state of Hidalgo, considered one of the centers of fuel theft.

Since taking office in December 2018, President Andrés Manuel López Obrador has made fighting fuel theft a central goal of his administration. But despite thousands of troops being deployed to guard pipelines, thousands of illegal taps are still found every year.

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In 2023, about 5,600 illegal taps were found nationwide. That was down from over 7,000 in 2022 but almost the same level as when López Obrador took office.

The government has cracked down on open sales of stolen fuel and managed to reduce the volume for a couple of years. Stolen fuels are often sold by the side of the road and sometimes through licensed gas stations.

Losses from stolen fuel at the state-owned oil company, Petroleos Mexicanos, dropped to as little as $275 million per year in 2019 and 2020. But since then losses have ballooned, rising to over $1.1 billion in 2022.

The pipeline taps cause violence between gangs and pose a risk to residents. To gain support among local people, thieves sometimes leave taps open.

On Jan. 18, 2019, an explosion at an illegally tapped pipeline in Hidalgo state killed at least 134 people. The explosion occurred in the town of Tlahuelilpan as residents collected gasoline leaking from the tap.