BOONE, N.C. (AP) — Inspectors checked a motel where three people were presumed killed by carbon monoxide fumes six weeks before anyone died, but their review didn't include investigating for the poisonous gas, the local health agency said Tuesday.

The Appalachian District Health Department said it inspected the swimming pool at the Best Western Blue Ridge Plaza in Boone six weeks before a Longview, Wash., couple were found dead of carbon monoxide poisoning in their motel room. Boone Police Sgt. Shane Robbins said the room is near the indoor pool, which is warmed by a natural gas heater.

Jeffrey Williams, 11, of Rock Hill, S.C., died Saturday in the same room where the Washington couple, 73-year-old Daryl Dean Jenkins and 72-year-old Shirley Mae Jenkins, died April 16.

A man answering the phone Tuesday at the offices of Appalachian Hospitality Management, which runs the Best Western Plus Blue Ridge Plaza, said company executives were referring questions to the Boone police.

The motel has been closed by police until at least Wednesday, when inspectors from the State Board of Examiners of Plumbing, Heating and Fire Sprinkler Contractors are due to arrive, Robbins said.

During a March 6 inspection, a health inspector noted that the motel violated a safety rule requiring ventilation of storage rooms where pool chemicals are stored, the department said in a statement released Tuesday.

The statement quoted the inspector's report as saying the room's ventilation problem "needs to be corrected asap."

"Consult inspector prior to making any installations," the report said.

The motel was not fined and did not face other consequences, but the chemical storage was to be revisited at the next inspection, health department spokeswoman Jennifer Greene said in an email to The Associated Press. Inspections are conducted at least twice a year, Greene said.

The agency's statement noted that "ventilation of any combustion gases from appliances is not part of the health department pool inspection." That includes the pool water heater, Greene said. She did not answer a question from the AP submitted by email and in a telephone voicemail about whether the water heater was located in the same room where the chemicals were stored.

Emergency responders found carbon monoxide in the room where they found Jeffrey Williams on Saturday, Boone police said. Jeffrey's 49-year-old mother, Jeannie Williams, was rushed to a hospital and survived. A preliminary autopsy found the boy died of asphyxia, which happens when toxic gases cut off oxygen to the body. State medical examiners will conduct toxicology tests on samples taken from the boy's body.

New toxicology results show the Jenkinses died of carbon monoxide poisoning, police said in a statement Monday. A regional pathologist's autopsies on the couple were inconclusive, police said.