( dpa )- A mysterious gas wafted through a Singapore shopping complex resulting in the hospitalization of 18 people with breathing difficulties, news reports said Tuesday.
The incident occurred when a man was sprayed with an unknown substance by two assailants, police said.
Six men, 11 women and an infant were taken Monday to Tan Tock Seng Hospital and Singapore General Hospital. Most were kept for observation overnight.
Tenants of the Golden Landmark Shopping Complex told The Straits Times that they had heard an argument near the entrance of the building.
Shortly afterwards, some began having breathing difficulties and rushed outside where they saw a man lying on the ground foaming at the mouth.
"I came out of my shop when it became difficult for me to breathe," Nizam Deem, the 50-year-old owner of a textile store, was quoted as saying.
Civil Defence Force officers, a hazardous materials response team, seven ambulances and two fire engines were sent to the scene. The building's security officers had evacuated nearly 100 tenants and shoppers by the time they arrived, the report said.
Tests run by the civil defence officers to determine the nature of the gas were unable to detect any trace of it, a spokesman said.
The building was re-opened in the evening.
A spokesman for the centre's management, who viewed closed-circuit camera footage of the incident, said a dispute had taken place between two-middle-aged men who were not tenants of the building. The gas incident appeared linked to the disagreement, he said.
Police were investigating the incident.