Police spent much of Sunday interviewing the boy’s family and other witnesses to learn why he slipped beneath the surface of the pool and remained under water for at least five minutes. He is being treated in the intensive care unit of Baystate Medical Center Children’s Hospital.The child’s name was not released because police have not finished their investigation, said Sgt. Doreen Mikan. The boy was attending a family gathering.High Meadow is a privately run summer facility that hosts family picnics and corporate events for a fee. During the week, it also operates a day camp for children.In addition to a full size swimming pool, it has a wading pool for young children. Police would not say which pool the boy was found in. The facility provides lifeguards, Mikan said.High Meadow was staffed adequately yesterday,” she said on Sunday. There were staff members there.”On Sunday, the metal gate in front of the facility’s driveway was closed and no one answered the telephone.Town Manager William Smith said he was surprised when police called to brief him about the accident.We haven’t had many emergency calls, especially of that nature, from High Meadow,” he said. Most of the complaints have to do with excess noise. Their record is impeccable. They’re very careful about life guarding and protection.”