At least 32 people were killed in Mexico on Sunday after the bus they were traveling in turned over on a wet road in the southwestern state of Guerrero, a Red Cross official said.
At least seven people were injured and believed to be in a serious condition, the official said. "In the area where it happened it's raining very hard," he added.
The official said most of the people inside the passenger bus were wearing T-shirts emblazoned with the logo of Mexico's Labor Party (PT), a small grouping in Congress supporting leftist presidential hopeful Andres Manuel Lopez Obrador.
Other emergency crews were dispatched to where the accident took place about 2-1/2 hours drive southwest of Mexico City.
Guerrero state police department had no immediate comment.
Mexico holds a presidential election on July 1.
Bus crashes and other road accidents are common on Mexico's main roads, causing hundreds of deaths a year.
In April, at least 43 people were killed when a cargo truck crashed into a bus on a highway in the Gulf state of Veracruz, in one of the worst accidents the country has suffered in recent times.