Search and rescue efforts continued through the night. The helicopter carrying four passengers over Ha Long Bay lost its signal 10 minutes after taking off from Tuan Chau Island Wednesday afternoon.
The office of the National Steering Committee for Natural Disaster Response, Search and Rescue deployed military forces to find the victims.
The SAR-411, Vietnam's largest search and rescue vessel, was deployed by the Vietnam Maritime Search and Rescue Coordination Center to participate in the operation.