(Reuters) -Confirmed deaths in the partial collapse of a condominium near Miami rose by four to 94 on Monday as identifying remains became progressively difficult with the recovery effort in its 19th day, Miami-Dade County Mayor Daniella Levine Cava said.

Due to the passage of time, recovery workers are leaning more heavily on the medical examiner’s office to identify recovered bodies, an undertaking that is “very methodical” and takes time, Levine Cava said at a briefing.

The number of people still unaccounted for dropped to 22 on Monday from 31 a day earlier, and may include some of the victims who have yet to be identified in the rubble of the 12-story oceanfront building in the town of Surfside that partially collapsed in the early morning hours of June 24.

“The process of making identifications has become more difficult as time goes on, and the recovery at this point is yielding human remains,” Levine Cava said.

With no survivors rescued from the ruins since the first few hours after the collapse, officials last week declared that their search effort had switched from rescue to recovery.

Surfside Mayor Charles Burkett said security is being tightened at the site due to the importance of the location to families who lost loved ones.

A debate has already begun in the community over what to do with the site, with some people eager for it to be turned into a memorial for the victims.

“It’s much more than a collapsed building. It is a holy site,” Burkett said.

(Reporting by Nathan Layne in Wilton, Connecticut and Barbara Goldberg in Maplewood, New Jersey; editing by Jonathan Oatis and Steve Orlofsky)