The death toll of a weekend bus accident in Brazil's Sao Paulo state climbed to 16 after one of the injured died Monday, authorities said.

Jucineia Justino Leal, 42, who was admitted in critical condition to Pirajussara General Hospital, died before dawn Monday after suffering two cardiac arrests, according to the state Public Health Department.

Meanwhile the family of public official Valeria Santos Leite, who was not on the original list of fatalities, identified her body among the dead, the department said.

Thirteen people were killed instantly early Sunday when the bus flipped over on the Regis Bittencourt highway and rolled into a 10-meter (32-foot) ravine.

Of the 32 people who were hospitalized, only 15 remain Monday under medical attention.

Police said the bus driver will be charged with manslaughter after some of the 55 passengers reported that he had fallen asleep at the wheel.

A preliminary investigation showed that the bus had no mechanical failures, that no other vehicle drove too near the bus and that the driver had not stepped on the brakes before it crashed down the ravine.

The driver, identified as Oseas dos Santos Gomes, who was released after suffering slight injuries, said he remembered nothing of the moments preceding the tragedy.

The bus left Curitiba on Saturday night and was scheduled to arrive in Rio de Janeiro on Sunday, police said. EFE