The prosecutor's office in Oaxaca said earlier in the day that 27 people had been killed and 17 more had been injured as a result of the bus crashing from a height of 10 meters (33 feet).
"Unfortunately, the death toll in a bus accident that happened this morning in the municipality of Magdalena Penasco has risen to 29," the ministry said on Twitter.
The bus of the Yosondua company heading from Mexico City to the municipality of Santiago Yosondua in Oaxaca crashed into a ravine while it was parked near a local church, local media reported. The prosecutor's office specified that the crash could have been caused by a malfunction.
The list of passengers, published by local media, showed that the bus was used by a group of Mexican tourists.