Tijuana

A crowded city bus veered off an unpaved road and crashed, injuring 57 people, authorities said Monday.

At least six of those injured were said to be in serious condition, although all were expected to recover.

Sunday’s crash came six days after a bus accident in Ensenada that left at least 16 people dead and more than two dozen injured. The two incidents involved different bus companies and were unrelated, authorities said.

Government transportation authorities were investigating the cause of the accident, which occurred shortly before 11 a.m. in the city’s La Mesa district.

Suspicion about the cause of the crash focused on the possibility that the bus--owned by a private transportation concern--may have been going too fast and was overcrowded. Seventy to 80 people were reportedly aboard the vehicle when it rolled off a road and down a hill, landing on its side, according to reports here.

Of those injured, many were treated at the scene. More than two dozen others were taken to local hospitals. Injuries included broken bones and cuts, officials said.