"We'll do a few more tests on the boiler. And we are examining the scene, considering every possibility," a police official said.

The pipe was found to have been dislocated from the exhaust gas pipe, apparently letting carbon monoxide into the guest room, where

10 boys from Seoul's Daesung High School had been staying since Monday.

They were found Tuesday lying on the floor of the duplex holiday lodge in the northeastern coastal city in Gangwon Province.

Three of them were dead, while the other seven were unconscious.

The boiler will be transported to the NFS for further examination once the on-site investigation ends, the police added.

The victims were on a trip to the famous getaway location to celebrate their last year of high school after taking the national college entrance exam.

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.

Later in the day, another student regained consciousness 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 measured at 155 ppm, nearly eight times higher than the normal level. (Yonhap)