Four people died and another five were seriously injured when a bus they were travelling on plunged into a 100-metre abyss Tuesday in northern Vietnam, a local official said Friday. The bus, driven by Hoang Van Dung, 35, left the road after Dung accelerated to free the front wheels from a rut in the newly built road in Tung San, a mountainous commune in Ha Giang province, 319 kilometers north of Hanoi, according to Trieu Tai Vinh, chairman of Hoang Su Phi district. "Of the total of nine people on the bus, four men, aged between 23 and 52, were killed instantly," Vinh said. "Five other passengers were seriously wounded and were rushed to the hospital in Hanoi. Two of them are in critical condition, including the driver Dung who suffered major head injures," the Chairman said. "All the nine people were officers from the Vietnam Railway Corp.," he added.