Some local media said the bus driver went through the crossing's lowered safety barriers just before the crash, but the bus company said the cause of the accident was not clear. Police have detained the two drivers who survived the crash.

Daniel Scioli, the governor of Buenos Aires province, described Sunday as "a day of mourning in the province and in the nation."

In 2007, more than 8,000 people died in road accidents in Argentina – an average of 22 per day.

Firemen walk near the rail crossing where a passenger train crashed into a bus in Dolores, Buenos Aires province March 9, 2008. (Xinhua/Reuters Photo)