Two people died and at least 16 more were hospitalized after they fell ill while sitting in a sweat lodge at a New Age retreat center in Arizona, the authorities said Friday.

The dead and injured were part of a group of about 48 people who were taking part in a ceremony on Thursday evening inside a sweat lodge resembling a large sauna at the Angel Valley Retreat Center in Sedona, the red-rocks-clustered resort town about 115 miles north of Phoenix. Officials with the Verde Valley fire department said Friday that the event had been going on for about two hours when several people fell sick, complaining of feeling light-headed.

When emergency crews arrived about 5:20 p.m., they found four people in such bad condition that they were flown to Flagstaff Medical Center, and about 14 others were in need of treatment, the authorities said. Two of the sick  identified only as a man and a woman  later died. Officials had not released the cause of their deaths as of Friday night.

That evening, at least three people were still listed in critical condition at Flagstaff Medical Center, the authorities said.