A bus travelling through the southern Mexican state of Oaxaca has crashed into a ravine, killing 27 people, authorities said.
The accident left 13 men, 13 women and an infant boy dead, Oaxaca Interior Minister Jesus Romero said in a press conference on Wednesday.
Another 21 people were injured, of whom 12 are in critical condition, Romero added.
The bus was heading from the capital, Mexico City, to Yosondua, a municipality in western Oaxaca, when the driver is believed to have lost control and crashed in the town of Magdalena Penasco around 6:30 am local time, Romero said.
An investigation has been launched into the cause of the accident, with early indications suggesting mechanical failure, he added.
"We deeply regret the accident that occurred in Magdalena Penasco," Oaxaca state Governor Salomon Jara wrote on social media, offering condolences to the families of the deceased.
"Our government personnel are already working on the rescue operation and to provide all the support to the injured people," he said.
Deadly road accidents are common in Mexico, usually due to high speeds, poor vehicle conditions or driver fatigue.
Many rely on buses, sometimes operated by small transportation companies serving remote communities with ageing vehicles.
Crashes involving freight trucks have also increased on the country's highways.
On Wednesday, a fiery smash involving cargo vehicles left eight people injured on a highway in the central state of Queretaro, authorities said.
In May, at least 18 Mexican tourists died when their bus plunged into a ravine in the western state of Nayarit.
In the same month, 13 people were killed when a passenger van and a semi-truck collided on a highway in the northeastern state of Tamaulipas.
Road safety campaigners have called for stricter regulations, such as a ban on trucks pulling two cargo trailers.