Story highlights Shootout in the Mexican state of Michoacan leaves 43 dead, officials say

42 gunmen and one federal police officer are killed

It is unclear who the gunmen were

(CNN) A three-hour shootout between Mexican security forces and unidentified gunmen Friday left 42 of the gunmen dead, as well as one federal police officer, officials said.

Three gunmen were arrested.

The lengthy firefight erupted in the town of Tanhuato, Michoacan state, when a joint force of federal and state security forces encountered the gunmen in the course of an investigation, Mexican National Security Commissioner Monte Alejandro Rubido said at a news conference.

The gunmen belonged to a criminal organization operating in the neighboring state of Jalisco, Rubido said, though he didn't name the group.

The commissioner's description of the gunmen contradicts earlier reports that described them as "armed civilians." At least two news agencies, Reuters and AFP, reported that the confrontation was between security forces and civilians. They cited unnamed Mexican officials.

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