At least 41 people were killed Monday morning at 2:00 a.m. local time when their bus flipped over and fell off a bridge, falling 65 feet into a riverbed below. The incident occurred as the bus, part of a caravan of three carrying police, was traveling near the town of Rosario del Fuente in Salta province, about 932 miles north of Buenos Aires.

"Between 50 and 60 border patrol officers were on board. Some are still trapped," provincial emergency director Ernesto Flores told the La Red radio station, according to Reuters.

The death toll has more than doubled from the last time a report about the incident was given by a local mayor. At the time, it was said that 20 had died. In the latest update, emergency chief Francisco Marinaro revealed that ten police officers were hospitalized, four of whom are in serious condition. 

Six people have been rescued from the wreckage so far, but local mayor Gustavo Solis noted that some people remain trapped and the death toll could rise, according to AFP.

As an investigation into the incident continues, there are still conflicting reports about what caused the bus driver to lose control of the vehicle. The BBC quotes a local police statement which claims that one of the bus' tires burst, while Solis said that the road where the accident occurred is known to be in poor condition.

 "Those of us who know the area try to avoid driving at night," Solis said.

Despite it being at night, police said that visibility was good at the time so they have not ruled out mechanical failure as a possible cause.