A tanker truck carrying tar slammed into a highway toll booth in Mexico that had been seized by protesting teachers, killing seven people and injuring 14, authorities in the western state of Michoacan said.
The accident occurred on a highway west of the state capital, Morelia, state prosecutors' spokesman Alejandro Arellano.
Most of the dead and injured were believed to be teachers whose union has been holding protests in the state but authorities have not confirmed their identities, Mr Arellano said.
Six victims so far had been identified by colleagues as junior high school teachers in the towns of Paracho and Santa Cruz Tanaco, union member Jorge Cazares said.
Teachers have been protesting in Michoacan over educational reforms that would reduce union power in hiring decisions and establish teacher evaluations.
Protesters in Mexico often seize highway toll booths, and sometimes demand drivers pay a small sum to drive through without paying a toll.
Union leader Juan Jose Ortega Madrigal called on authorities to do a thorough investigation and demanded that the transportation company that owned the truck pay for funerals and medical expenses.