The bodies were found in the most heavily damaged section of the Mizpah Hotel, an 84-year-old Reno landmark, said Fire Department spokesman Steve Frady.
"The potential for location of additional victims in the debris-covered areas of the building still exists," Frady said, adding that the recovery effort will continue at least through Monday.
The search Sunday focused on the most dangerous section of the hotel, where the Halloween night fire destroyed floors, weakened walls and caused a huge debris pile, he said.
It has been proceeding slowly because that portion of the brick building had to be stabilized, he said.
"There's a tremendous amount of potentially dangerous situations in there and we're closely monitoring it so no one on the recovery team becomes a victim," Frady said.
Nine bodies were previously recovered, including three on Saturday. The deadliest fires in Reno before the hotel fire — a 1962 blaze at the Golden Hotel and 1879's "Great Fire of Reno" — each killed six people, said Guy Rocha, the state archivist.
Only four victims have been identified, a coroner's office staffer told the Reno Gazette-Journal, and some of the bodies were so badly burned that even their gender could not be determined.
At least 30 people were injured in the Mizpah fire, three critically. Police said 60 to 80 people had been inside the $150-a-week hotel, which mostly served boarders.
Makeshift memorials featuring flowers, candles and banners have been erected outside the casino-district hotel. "I love you, Chris," said one. "So sad you're gone," read another.
Police arrested a casino cook and paroled killer, Valerie Moore, who they suspect started the blaze by igniting a mattress.
Moore, 47, was being held without bail on a parole violation while the investigation continues, said Washoe County District Attorney Richard Gammick.
Fire officials have said the Mizpah had smoke alarms but not sprinklers, which was allowed by city code because of the building's age.
Frady said Sunday that city officials recommended in March that a potential buyer install sprinklers, but the recommendation was not imposed because the sale did not go through.
He said the hotel had been inspected 12 times this year — the last time just a few days before the fire — and was in compliance with city fire codes.
The recently renovated Mizpah was built in 1922 and placed on the National Register of Historic Places in 1984.