MEXICO CITY, June 19 (Xinhua) -- At least nine people were killed and another 12 injured after a bus overturned in the northwestern Mexican state of Sonora, federal police said on Tuesday.

The accident took place around 10:45 p.m. local time Monday night close to the city of Caborca, said the police.

Four men and three women died at the scene, while emergency services evacuated 14 passengers to hospitals in Caborca and Hermosillo, the state capital. According to local press, two of the injured were pronounced dead later on Tuesday.

Local press also reported that the bus carrying 21 passengers left the border city of Tijuana in the northwestern state of Baja California traveling to Guadalajara, the capital city of western state of Jalisco.

Survivors said that the bus veered off the road and overturned several times before coming to a stop on its side. Several passengers needed to be rescued from inside the bus.

The governor of Sonora, Claudia Pavlovich, offered her condolences to families who lost their relatives and said that authorities were continuing to administer medical services to the injured.

According to federal police, officials from the Sonora prosecutor's office were currently investigating to ascertain the cause of the accident.