Mexican authorities say federal riot police will stay in the town of Oaxaca until order is restored.
Police took control of the city Sunday, ending five months of sometimes violent protests by striking teachers and other groups who took over streets and buildings and called for the resignation of the state governor.
Witnesses say at least one person was killed as police broke through street barricades and turned water cannons on demostrators.
President Vicente Fox ordered federal action after a U.S. activist-journalist and two Mexican men, one of them a teacher, were shot and killed Friday near the site of the protests.
Leaders of the teachers union said Monday they plan further marches. They had earlier agreed to go back to work, but it is unclear if classes have resumed for the more than a million public school students in Oaxaca state.
Some information for this report provided by AFP and Reuters.
