Among the victims were 10 men and three women. Authorities did not report any wounded state police.
The San Luis Potosi state prosecutor’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 member of the state police and a relative earlier Thursday, the office said.
In the southern state of Guerrero, authorities said Friday they had found six bodies with bullet wounds and two heads nearby.
The Guerrero state prosecutor’s office said the remains were found near a burned out and shot up vehicle in the municipality of Quechultenango.
Mexico President Andrés Manuel López Obrador continues to face stubbornly high rates of violence more than midway 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 can’t confront violence with violence, coercive measures are not enough, that is the conservative, authoritarian vision,” López Obrador said last month.