Four gold prospectors and a rescuer have died from suffocation in a cave in the northeastern province of Cao Bang, online newspaper Dan Tri reported.
On Tuesday afternoon, a group of around 10 gold prospectors sneaked into a deep cave in a rural village with the hope of finding gold.
Trieu Chong Hin, Trieu Ton Phan, Trieu Van Chieu and Dang Van Tinh then suffocated and died at the cave's bottom.
One day later, Trieu Van Dung, a local militiaman, also suffocated to death while making his way into the cave to rescue the victims.
Local authorities said rescuers could not go deep into the cave given the high levels of toxic substances in the air.
The bodies of the dead victims have yet to be recovered.