More than 100 emergency worker responded to a chemical spill on board a container ship on Monday morning.
The accident happened at about 6.40am, as the 92,000-tonne Maersk vessel was entering Hong Kong waters coming from Shanghai.
It was directed to an anchoring area south of Lamma Island, reserved for dangerous cargos, at about 7.30am.
A Government Flying Service helicopter was deployed to offer medical help to three crew members who complained of feeling unwell. But they declined the offer and the helicopter left.
Three fireboats were sent to the scene, and three fire engines and three ambulances were on standby in Central, the Fire Services Department said.
Firefighters, wearing suits to protect them from chemicals, went on board to check the situation while two police launches kept other boats away.
It is understood to be a minor chemical spill.
Around noon, officers from the Fire Services Department and Marine Department were still investigating the case.