A Mexican human rights group has accused police of raping or sexually abusing almost two dozen women during riots in San Salvador Atenco last week.
Police stormed the town after six officers were taken hostage
The National Human Rights Committee, a government agency, said police raped seven and sexually abused 16.
The assaults are said to have occurred when the women and many others were held during the unrest, sparked by a round-up of unlicensed street vendors.
The Mexico state police chief has denied the charges.
Three of the women who were allegedly assaulted are foreigners.
One of them, Valentina Palma, a Chilean studying cinematography in Mexico, told La Jornada newspaper that she was robbed and beaten by officers.
"They insulted me, groped me, anything they wanted," she was quoted as saying. "When they jailed me that was when I saw the girls with their pants and underwear torn, sobbing."
Hundreds of police stormed the town after machete-wielding farmers kidnapped and beat six policemen who had been detaining the unlicensed flower vendors.
A teenage boy was killed and dozens of people were injured in the riots which lasted throughout Wednesday.
The six police officers taken hostage by the rioters were released, but up to 50 police officers were injured in the clashes - a number of them seriously.
Television images of police beating bound demonstrators caused a national outcry after the riots.
The BBC's James Hider in Mexico City says the new allegations are fuelling fears of more violence before the presidential elections in July.