The accident occurred at about 3.30am when a container truck hit the rear and smashed the 7-seat van that had stopped at traffic lights at the intersection in front of the Linh Trung Industrial Park in Thu Duc District's Linh Trung Ward.
Huynh Van Tiep, 55, a cousin of the victims of the accident, who was on 45-seat coach stopping in front of the van, said his cousin's family had rented the coach and the van to take their relatives on a pilgrimage to a pagoda in Dong Nai Province.
Three of the victims on the van were Americans of Vietnamese origin who had returned home three days earlier, Tiep was quoted by VnExpress as saying.
He said the driver of the container truck had shouted: "the brake didn't work", before running away from the site.
The 48-year-old driver of the container truck, Vo Van Rang, presented himself to Thu Duc District police later on May 31.
Nguyen Ngoc Tuong, deputy head of Ho Chi Minh City's Board for Traffic Safety, said this was the most serious traffic accident that had occurred in Ho Chi Minh City so far this year.
According to the latest information from the National Traffic Safety Committee, the container truck was driving at 55km per hour. Driver Rang also reportedly told the police that the he had lost his brakes and was unable to stop it.
In a report sent to the Transport Ministry, the Vietnam Register said that the container truck was due to be serviced the day after the accident. The truck was manufactured in the US and had been checked on March 2.
Deputy Prime Minister Nguyen Xuan Phuc, chairperson of the National Traffic Safety Committee, visited the victims' families on May 31 and asked police to investigate the accident and prosecute those responsible.