Students clashed with members of the National Guard and state police at a toll plaza near Chilpancingo, Guerrero, on Friday.
At least 14 guardsmen sustained burns from molotov cocktails and one fractured his ankle, the National Guard said.
Seventeen police were also injured, said Public Security Minister Evelio Méndez Gómez.
The confrontation occurred at the Palo Blanco toll plaza on the Autopista del Sol, the highway that runs between Mexico City and Acapulco.
Students from the Ayotzinapa teacher training college – the school attended by the 43 young men who disappeared in Iguala, Guerrero, in 2014 – arrived at the plaza, located about 60 kilometers south of the Guerrero capital, with the intention of occupying it, presumably to collect tolls from motorists.
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The early afternoon clash, which reportedly lasted close to an hour, occurred after security forces tried to persuade the students to leave.
The newspaper Milenio reported that the students used stones, firecrackers and molotov cocktails against the security forces.
They also traded blows with the guardsmen and police, and pushed a driverless semi-trailer toward them with the aim of injuring or intimidating them. The truck crashed into a food stand but no one was injured, the newspaper El Financiero said.
The security forces deployed tear gas to repel the students.
Five students were detained, but they were subsequently released following mediation by National Human Rights Commission officials, Méndez said. The majority of the Ayotzinapa students left the toll plaza on the same buses on which they arrived.
El Financiero reported that the students have been occupying toll plazas at least twice a week for six years. Security forces stopped them from doing so for the first time last Friday, after the Senate passed a law that punishes the occupation of toll plazas with up to seven years’ imprisonment, the newspaper said.