Two of the victims were men and two were women, but Dubbs did not know whether the fifth victim was male or female.
Dubbs said he did not know the conditions of the people.
The borough's gas department shut off service to the house and indicated to Dubbs that a blocked chimney was the cause of the carbon monoxide gas backing up into the house.
Dubbs said there was a gas furnace on the first floor with a metal pipe connecting the furnace to an old chimney.
"There was a lot of soot built up around where the flue went into the chimney," Dubbs said.
A woman living across the street said she did not know the names of the people, who she said moved in at the beginning of the month. Another neighbor said he also did not know who lived in the house.
The people were flown by helicopters to three hospitals, with two of the victims going to the University of Pittsburgh Hospital, Chambersburg Police Sgt. Richard Swartz said. He said he did not know to which other hospitals the patients were taken.
The patients were flown to hospitals with hyperbaric chambers, Dubbs said.
A hyperbaric chamber allows the air pressure to be raised above the normal level to treat conditions in which a high concentration of oxygen is needed. That or 100 percent oxygen treatment is used to bring the oxygen content of the blood back to normal, according to WebMD.
The Web site scuba-doc.com lists hospitals with hyperbaric chambers in Pennsylvania, including facilities in Allentown, York and Pittsburgh. Washington County Hospital in Hagerstown has a chamber, according to the Web site.
Dubbs said property owners should have their chimneys cleaned if they use gas, oil, wood, coal or other combustible fuel for heat. Soot buildup, birds' nests and other obstructions can cause a blockage that could prove fatal, he said.
The symptoms of carbon monoxide poisoning at moderate levels include severe headaches, dizziness, shortness of breath, nausea and disorientation and can be fatal if exposure is prolonged, according to the U.S. Environmental Protection Agency. The EPA recommends that homes be equipped with carbon monoxide detectors.
About 200 people die each year of carbon monoxide poisoning in the United States and thousands of others go to hospital emergency rooms, according to the Consumer Product Safety Commission. Levels above 150 parts per million can result in unconsciousness and death, according to the commission.