MEXICO CITY (AP) — Mexico’s National Guard said seven gunmen and one of its officers died in a shootout Tuesday in the north-central state of Guanajuato. A second officer was wounded.

Authorities said the suspects opened fire on a National Guard patrol on a highway near the city of Irapuato and the officers returned fire.

Guanajuato was once considered a relatively peaceful agricultural and industrial state. But so far this year it has registered more homicides than any other state in Mexico, including some with much larger populations. The state recorded 3,211 homicides in the first 11 months of the year, well above the second most violent state, Baja California.

Much of the violence in Guanajuato is caused by gangs that steal fuel from government pipelines. Since the government cracked down on the illegal taps, the gangs have unleashed a campaign of extortion and killings.

Nationwide, the number of homicides in the first 11 months of the year rose 2.7 % from the same period of 2018.

The federal government says about 40% of all homicides nationwide are concentrated in about 30 cities and townships. For example, the Pacific coast port city of Manzanillo had a homicide rate of 121 per 100,000 residents so far this year, while the border city of Tijuana had a rate of 105 per 100,000 and nearby Playas de Rosarito had 126.5 per 100,000.