The attack occurred in a neighborhood in the town of Salamanca, with a statement from the mayor's office saying that officials launched an operation to find those responsible for the assault.
"The deaths of 11 people have been confirmed, 10 of whom died at the scene and one more while receiving medical attention at a hospital," the statement said.
"Additionally, 12 people were injured by gunfire and are receiving medical attention," it added.
Four bags containing human remains were also found Saturday night in the same town.
Guanajuato is a thriving industrial hub and home to several popular tourist destinations, but also remains the country's deadliest state due to gang turf wars, according to official homicide statistics.
Mexican President Claudia Sheinbaum said at the beginning of the year that Mexico's homicide rate in 2025 had fallen to its lowest level in a decade, as a result of her administration's national security strategy.