Mexico kicked off Independence Day celebrations Thursday night.
Shortly before midnight in Mexico City, President Felipe Calderon gave the call to arms "El Grito," before thousands of revelers under heavy police security.
There have been no reported incidents in the capital.
But in the small western town of Morelia, gunmen threatening to attack people forced police to call off part of the celebration. There were no reports of anyone being injured.
The incident is under investigation.
In the past, some celebrations marking Mexico's fight to separate from Spain have been marred by deadly violence, including a 2008 grenade attack in Morelia that killed eight people and wounded dozens of others.