Le Van Thai, deputy director of the Saigon Railway Operations Branch, said the southbound SE5 train was passing through Dau Giay-Long Khanh at around 4 pm on August 15 when a stone shattered a carriage window.
The incident was reported to the station manager when the train reached Bien Hoa Station at around 6 p.m. The manager then alerted Long Khanh Station, which contacted local police.
As it was already dark when the incident was reported, railway staff and police inspected the railway section the following morning in an effort to identify the person responsible.
Thai said investigators suspected the stone was thrown near a cemetery in Long Khanh Ward, where several bricks were found. Footage from a camera on the locomotive showed no suspect.
Railway officials believe the person may have waited until the locomotive had passed before throwing the stone, leaving the incident outside the camera's view. There were also no nearby residential security cameras covering the railway.
Authorities and Long Khanh Station are continuing their investigation, but no suspect has been identified. No passengers were injured.
Thai said railway authorities regularly work with residents living along railway lines to raise awareness and secure commitments to protect railway safety corridors.
Despite these efforts, similar incidents still occur, he said, adding that Long Khanh Station had been asked to continue working with police on the investigation.