A truck and trailer collided last night with a bus filled with junior high school students on their way home from a field trip, killing 23 people, most of them 15-year-old children, and injuring 29 in Greece’s worst traffic accident in recent memory. It occurred shortly before 8 p.m. at the Vale of Tempe, a ravine on the highway linking Athens and Thessaloniki, about 380 kilometers (235 miles) from the capital. The accident shocked Greece and plunged the small farming community of Makrihori into mourning. The children were from the First Lyceum of the small town of about 3,000 people near Veria in northern Greece. They were returning from a three-day school trip to Athens. Initial reports were confused, with dead and injured being sent to different hospitals and with the numbers of student casualties and adults hurt or killed in the crash not immediately distinguishable. Police and fire department officials said that the bus was carrying 49 students, three teachers and the driver. The National First Aid Center (EKAB) chief, Christos Ressos, said that 20 people were killed and 35 injured. But at 11.20 p.m. state-run NET television reported the Larissa Hospital said it had 17 dead. The hospital at Katerini said it had six dead. The total of injured was reported to be 29. Earlier, a spokeswoman at Larissa Hospital said three or four of the injured in her hospital were in critical condition. It was not clear whether they were now included among the dead. Doctors said most of the victims had suffered massive head injuries. The images of the bus, which resembled the result of a bomb attack, pushed the Iraq war and all other news off television broadcasts. The Athens News Agency quoted traffic officials saying this was the worst road accident since the end of World War II. «I have seen very many accidents, I have seen the results of earthquakes. But in 33 years as a fireman, I have never seen such an accident,» the fire department’s deputy chief, Georgios Georgiakos, told state-run NET television. The causes of the crash were not yet known, but reports from witnesses as well as hypotheses by police and fire department officials described the following chain of events. A truck and trailer heading downhill through the pass, carrying a load of large plywood boards from Thessaloniki to Athens, veered out of control and swung into the oncoming bus. Plywood boards appear to have sliced through the bus, breaking the roof’s supports and bringing it down on the heads of its occupants. The bus veered off the road and smashed into an embankment. The truck then hit three cars that were behind the bus, smashing all of them and causing two to burst into flames. It was not clear late last night how many of the victims were from the cars. «The picture is three cars smashed, two of them burned. And a bus that has disintegrated,» Georgiakos said. The truck driver was described as a young man (some reports said he is 22) named Dimitris Tollas. He was slightly injured and was arrested. «He is being held,» said Christos Iordanidis, Larissa’s police chief. «I can’t say anything about the cause of the crash. It is being investigated.» Suspicion, however, focused on the possibility of the plywood boards not being tied down. Nikos Gesoulis, the deputy education minister, who was at the scene of the accident, said, «It is one of the worst days for Greece’s schools… I hope we never see a day like this again.» On February 22, an intercity bus crashed into the Aliakmon River near Thessaloniki, killing 16 people.