A ski tour bus that crashed Friday in Nagano Prefecture killing 15 people on board steered an eratic course for several hundred meters before it crashed, indicating the driver may have lost control of the vehicle, transport ministry sources said.

The information was revealed after police and ministry inspectors analyzed images captured by a roadside surveillance camera installed 250 meters before the crash point. The bus was also traveling at more than 50 kph on a slope down to the site of the crash.

Separate information indicates driver Hiroshi Tsuchiya, 65, who was killed in the accident, had not received adequate training, leading police to suspect the bus operator may have allowed an unskilled driver to take the wheel.

When Tsuchiya was hired by the Tokyo-based bus company ESP, he said during a job interview, "I'm not good at driving a large bus," according to ESP sources.

In last week's accident, two drivers and 13 university students were killed when the bus carrying 39 passengers from Tokyo to a ski resort in Nagano Prefecture veered off the road and rolled over.