The driver of a truck that a late-night intercity bus had apparently been in the course of overtaking just before driving off a bridge into a river in northern Greece nearly six weeks ago, shares responsibility for the accident that caused the deaths of 16 people, according to the results of a police investigation leaked yesterday. But sources at the Katerini Traffic Police Department, which is handling the investigation, refused to expand on the exact involvement of truckdriver Michalis Constantinopoulos, 45, in the February 22 accident. Fifteen of the 23 people on the bus, including driver Christos Tolios, 38, were killed in the 15-meter fall into the Aliakmon River, while another passenger died in the hospital 10 days later. The bus had been heading from Thessaloniki to Athens. Initially, police had laid the full blame on Tolios who, according to survivors, had tried to overtake the truck.