Three Police Tactical Unit (PTU) officers collapsed in the heat during an anti-riot exercise yesterday. The three men were drilling with 38 other officers at the PTU headquarters in Fanling. The women officers taking part completed both the morning and afternoon training sessions. The first officer was struck down at 11.45am, with his colleagues following minutes later. They were given first aid by physical training instructors before being taken to North District Hospital. Two of them were discharged after treatment while the third man remained under observation last night. 'They were doing a basic internal security anti-riot drill on the open-air drill square,' Superintendent Charles Alison, from the PTU's training wing, said. 'They were wearing anti-riot helmets, shields and carrying riot weapons like shotguns.' Mr Alison said during the morning sessions between 9.30am and 12.30pm, there were breaks every 15 to 20 minutes. The exercise, a routine part of the 12-week training course, involved 41 police officers from the PTU Charlie Company's Team 2. They started training two weeks ago. A police spokesman said that during hot weather, training instructors would increase the number of breaks for participants to drink water during exercise. In February, Superintendent Wong Wing-kei collapsed and died during a PTU training session in Fanling. Initial autopsy results indicated he had suffered a heart attack.