MEXICO CITY (AP) — Mexican authorities said they rescued 42 hostages, including 18 children, from criminal groups Saturday after a wave of kidnappings in Sinaloa state, where more than 600 special force troops were sent to beef up security.

Sinaloa Gov. Rubén Rocha said an intensive operation by police and military forces was still trying to find 24 more people who were kidnapped.

Kidnappings en masse took place Friday in different areas of the La Noria region, outside Sinaloa’s capital city of Culiacan. Members of criminal groups made hostages of at least three families, local public security chief Gerardo Mérida said.

Federal authorities sent special forces troops to Sinaloa to search for the missing people. An additional 300 soldiers and a National Guard battalion are also operating in the area.

Local authorities have not said who was behind the mass kidnappings, which took place one day after three people were killed in the state’s Badiraguato region.

Culiacan and other cities in the state have been the scenes of violent incidents in recent years, with killings by members of the powerful Sinaloa cartel.