The incident happened after another health worker had fainted in the same ambulance a day earlier. His condition is reported to be stable.

Negeri Sembilan fire and rescue department assistant director of operations Ahmad Mukhlis Mokhtar said rescuers were rushed to the scene after receiving a call about the incident at about 9.50 am.

“Preliminary investigations by the hazardous materials (Hazmat) unit found that there were no leaks in the area of the health clinic other than the oxygen level in the building being normal. Preliminary information also found that the four victims had fainted in the ambulance,” he told reporters here.

Meanwhile, the Hazmat unit head Mohammad Idris said the 29-year-old victim had initially complained of chest pain before fainting at the clinic while the three others, who were his colleagues, lifted him into the ambulance to be sent to the Port Dickson Hospital, which is 33km away.

“However, upon arrival at the hospital, when the back door of the ambulance was opened, the three others who were with the victim were also found unconscious while he had died,” he said.

It normally takes an ambulance about 20 to 30 minutes to get from the clinic to the Port Dickson Hospital.

Mohamed said the cause of death of the victim could not be determined yet.

He said the driver and another staff member at the front did not suffer any problems and that the three other victims were in stable condition.

He added that further investigations were still ongoing but confirmed that the ambulance’s exhaust system was leaking.