Eleven people were killed and at least 12 others were injured when gunmen arrived at a soccer pitch and opened fire in the state of Guanajuato on Sunday.

Six people were still receiving medical attention for injuries, Guanajuato’s state attorney general’s office said in a statement on Sunday evening.

The massacre occurred in the community of Loma de Flores, in the municipality of Salamanca, just 12 kilometers (7.5 miles) east of the city of Irapuato. 

According to local residents, more than 100 gunshots were heard during the attack, causing widespread panic among those who were lingering at the field after an amateur soccer match between two local teams had ended.

Salamanca Mayor César Prieto condemned the attack and said it was part of an ongoing “crime wave” in the city and appealed to President Claudia Sheinbaum for help to control the violence.

“The Municipal Government of Salamanca expresses its most sincere solidarity with the families and people affected by these events, and reaffirms its commitment to support them and work permanently for the safety and peace of our community,” the mayor said in a press release.

In a social media post, Guanajuato Governor Libia Denisse García Ledo described the events as “unacceptable,” and declared that state authorities “will act firmly to protect the families, restore peace to the community, and bring the perpetrators to justice.”

The Guanajuato state prosecutor’s office said it was investigating the attack while also coordinating with federal authorities to reinforce security in the area. The motive for the attack remains unclear.

Asked at her Monday morning press conference for information about the attack, President Sheinbaum deferred to the state attorney general’s office, though she said her government is coordinating with the local authorities. 

The incident received broad international coverage as Mexico is due to host 13 soccer matches during the FIFA World Cup this summer.

Guanajuato, the sixth most populous state in Mexico with just over 6 million residents, registered the highest number of murders in the country last year, with 2,539 homicides recorded, representing 10.9% of the national total.

A local criminal organization, the Santa Rosa de Lima cartel (CSRL), which primarily engages in oil theft, has been battling the powerful Jalisco New Generation Cartel (CJNG). Salamanca, home to a Pemex oil refinery, has been particularly subject to violent gang-related attacks.

Several violent incidents were reported in Salamanca on Saturday. At least five men were killed and another was abducted.

With reports from Proceso, BBC, Quadratín Jalisco, La Jornada and NBC News