Among the victims were 10 men and three women. Authorities reported no injuries to state police.
The San Luis Potosi state attorney’s office said weapons, tactical gear and vehicles were seized. Thursday’s operation was the result of intelligence gathered after police arrested four people as they buried a state trooper and a relative earlier Thursday, the office said.
In the state of Guerrero, in the south of the country, the authorities announced on Friday that they had found six bodies with gunshot wounds and two heads nearby.
The Guerrero state attorney’s office said the remains were found near a burned and shot vehicle in the municipality of Quechultenango.
Mexican President Andrés Manuel López Obrador continues to face stubbornly high rates of violence more than halfway through his 6-year term. The president has emphasized attacking violence with social programs rather than head-on confrontations with the country’s powerful drug cartels.
“I am absolutely convinced that you cannot confront violence with violence, coercive measures are not enough, that is the conservative and authoritarian view,” López Obrador said last month.