Police in the northern province of Quang Ninh said the two survivors of a karaoke tragedy that left 10 dead cannot assist them in their investigation.
On September 8, employees of the Queen Club karaoke parlor in Hai Ha District found 11 men and one women lying unconscious in a room they'd rented the night before to sing karaoke.
Six of the victims were pronounced dead at the scene. Six others were rushed to hospital and four have since died.
Cao Van Nam, 26, was the only victim to recover. He can talk, but cannot remember what happened.
Doctors said Nam suffers from short-term amnesia.
Pham Van Tuan, the other surviving victim, remains in a coma.
Police believe the 12 revelers passed out after dragging a gas-powered generator into an enclosed karaoke room late on September 7 and breathing the fumes.
The police said they are still collecting evidence to determine the cause of the accident.