CANCUN, Mexico — Driver negligence and speed caused a bus crash in southern Mexico that killed eight Americans, two Swedes, one Canadian and a Mexican tour guide as they traveled from cruise ships to visit nearby Mayan ruins, officials said Wednesday.

Quintana Roo state prosecutors said a preliminary manslaughter investigation indicated the driver lost control of the bus and when he tried to get back on the narrow highway, the bus flipped, struck a tree and landed in vegetation along the roadside.

“Due to a lack of care the driver lost control of the bus’ steering to the right, leaving the asphalt,” state prosecutor Miguel Angel Pech Cen said at a news conference. He said evidence found at the scene indicated the driver was going too fast.

The state government said that in addition to the 12 people killed, three Canadians, four Brazilians, four Americans and two Swedes had to be hospitalized for treatment of injuries. The two Swedes were transported to the United States for treatment. Seven other people were slightly injured in Tuesday’s accident and returned to their cruise ship.

By Wednesday afternoon, only four tourists – one Brazilian and three Americans – remained in local hospitals, the state prosecutor’s office said.

A state government statement early Wednesday said the bus driver was injured and taken into custody. But Pech Cen later said the driver was not in custody but was transported from the scene for medical treatment