Two months ago, an elderly couple passed away in room 225 of the Best Western in Boone, N.C., a small town nestled in the foothills of the scenic Blue Ridge Mountains. The incident, while mysterious, was largely chalked up to old age until 11-year-old Jeffrey Lee passed away in the same room this past Saturday. His mother remained hospitalized on Monday and had no recollection of what had happened, according to police reports.

Many said the room was simply haunted, but others in the small town knew there had to be a more practical explanation -- and, of course, there was. On Monday afternoon, the local police department named the culprit: carbon monoxide. The mystery might have been solved, but questions remained as to why it took investigators and medical examiners several weeks to identify the problem, and why dozens of guests were allowed to stay in room 225.

“It has been widely reported that in an earlier incident on April 16, 2013, Daryl Dean Jenkins, 73 years of age, and his wife, Shirley M. Jenkins, 72 years of age, were found deceased in the same room,” Police Sergeant Shane Robbins said on Monday. “The regional pathologist reports that on April 17 and 18, 2013, Mr. and Mrs. Jenkins were autopsied. Results at that time were inconclusive. Samples were sent to the Office of the State Medical Examiner for toxicological analysis. Results of that analysis were received within the last 24 hours. After receiving those results, the cause of death in both cases was determined to be carbon monoxide toxicity.”

Investigators told local CBS affiliate WBTV that they had requested results from the State Medical Examiner’s office for several weeks but got no response. “The last letter was sent on May 29, but we didn’t hear back from them,” Police Captain Andrew Labeau said. The boy died in room 225 10 days later.

“It is simply inconceivable that the hotel would choose to rent the same room to others while toxicology results were pending related to the deaths of Daryl and Shirley,” the Jenkins’ family lawyer said in a prepared statement.

Moreover, documents obtained by the Charlotte Observer indicate that health inspectors had found deficiencies at the Best Western’s indoor swimming pool earlier in the year. According to the paper, the health inspector indicated that the pool’s chemical and equipment room needed better ventilation, writing, “This needs to be corrected ASAP.”

It remained unclear what role the deficiencies may have played in the deaths, though the police report said Room 225 lies directly above the pool’s natural gas heaters. The Best Western remained closed pending an inspection Wednesday from the state board overseeing plumbing, heating and fire sprinkler contractors.

Carbon monoxide is often called the “silent killer” as it is a tasteless, colorless and odorless gas produced by incomplete combustion in fuel-burning devices like boilers and heaters for water and swimming pools, furnaces, and cars. Victims typically have no idea that they are being poisoned and often lose consciousness as it starves their respiratory system of oxygen.

A USA Today investigative report in January claimed that eight people had died and at least 170 others were hospitalized for carbon monoxide poisoning at hotels over the past three years. Nationwide, as many as 500 deaths per year are attributed to carbon monoxide, according to the Environmental Protection Agency. Another 20,000 people end up in the emergency room.

North Carolina, like many states, does not require carbon monoxide alarms in hotels, though organizations like the Carbon Monoxide Safety Association are out to change that. However, they face an uphill battle. An industry analyst told USA Today in its report that hotels are unlikely to voluntarily add alarms in every room anytime soon because they cost up to $100 apiece and must be replaced every five years. The analyst added that being poisoned in a hotel room is as rare as “being hit by a meteor.”