(ATTN: RECASTS headline, lead; UPDATES with official police conclusion on cause of deaths in paras 2-6; TRIMS)
GANGNEUNG/SEOUL, Dec. 19 (Yonhap) -- Police concluded Wednesday that the three high school students found dead in a guesthouse in Gangneung were killed by carbon monoxide poisoning.
Police announced the official result of their investigation into the deadly incident that also left seven others unconscious. Two of them have recovered consciousness following hours of intense treatment.
Ten boys were found Tuesday lying on the floor of the duplex holiday lodge in the northeastern coastal city in Gangwon Province. Three of them were immediately pronounced dead.
The Daesung High School students from Seoul were on a trip to the popular getaway location to celebrate their last year of high school after taking the national college entrance exam.
Police said the room where the victims had been staying had a carbon monoxide concentration level of 48-63 percent. A level of 40 percent is considered fatal.
Autopsies of the victims' bodies will not be carried out, in accordance with their parents' requests, they added.
Police earlier confirmed a defect in the gas-fired boiler at the guesthouse in their joint probe with the National Forensic Service (NFS) and the Korea Gas Safety Corp.
They turned the boiler on to see how it operated and found that it was emitting a large quantity of exhaust gas from a faulty pipe,
The pipe was found to have been dislocated from the exhaust gas pipe, apparently letting carbon monoxide into the guest room.
The government has vowed all-out efforts to provide every means of support possible in helping the victims and their families.
"We will spare no efforts in assisting the victims' families and will make sure each ministry and government agency does their job meticulously as soon as we learn the exact cause," Education Minister Yoo Eun-hae said earlier.
Although the Seoul Metropolitan Office of Education is in charge of matters pertaining to the accident, the ministry will oversee the investigation and take charge during the aftermath process, Yoo said.
Early Wednesday, one of the survivors recovered to a stage where he could say his name and answer simple questions. Another student regained consciousness later and is now stable enough to drink water, the police said.
The rest are in intensive care units in two different hospitals and are undergoing treatment in high-pressure oxygen chambers.
Police and firefighters have suspected a fault in the ventilation system as a possible cause. The forensic team had discovered a disconnected part in the pipes. No alarm system for gas leaks was installed at the guesthouse.
The level of carbon monoxide inside the house was initially measured at 155 ppm, nearly eight times higher than the normal level.
(News Focus) Termination of military pact with Japan raises concerns over S. Korea-U.S. alliance
Another new missile highlights N.K.'s focus on conventional weapons amid nuclear talks
Trump's pressure on S. Korea raises concern about U.S. interests, alliance
Latest test indicates N. Korea's successful development of new ballistic missile: experts
Seoul-Tokyo ties tipped for deeper rift after Japan's expanded export control: experts