Family members of a couple missing in the Florida condo collapse continue to receive phantom phone calls from their landline. Experts don’t know why.

• The family of a couple still missing in the Florida condo collapse keeps getting calls from them.
• The calls come from a landline, but experts don't know why, The Washington Post reported.
• Officials said they can't locate the couple in the area where their apartment may have fallen.
• Visit Insider's homepage for more stories.

The family of an elderly couple still missing in the Florida condo collapse is getting phone calls from their landline number and experts aren't exactly sure why, The Washington Post reported.

At least 12 people have been confirmed dead, with 149 still unaccounted for after the Champlain Towers South collapsed early Thursday morning.

Arnie and Myriam Notkin's phone was right next to their bed, but officials said rescuers "exhausted all of our resources trying to verify" that either or both of them were still alive, but picked up no signs of life in the area where they believe the couple's apartment may have collapsed.

"I don't know how they're getting the call," former Miami-Dade fire chief Dave Downey told the Post. "It really doesn't make any logical sense how you'd be dialing a phone if you were trapped. But we put resources on the area where the apartment was, and we have not found anything."

Experts don't know what's behind the calls and the family hopes it's not "a sick prank."

Downey, who assisted during the 2010 earthquake in Haiti, said similar incidents happened then but they were later discovered to be calls and texts sent days before and were merely stalled.

Ted Rappaport, an electrical engineering professor at New York University, told the Post this sort of thing usually only happens with cellphones, but the number the family is getting calls from is a landline.

Calls returned to the landline end in static or a busy signal. No one has actually spoken on the other end of the line.

Rapport said it could be a technical issue brought on by the collapse, but he was also skeptical because the call goes to the same number and no other families reported getting any calls from those still missing.

He also suggested several other technical issues that could cause the static or lack of noise on either end of the line, but the probability of those scenarios isn't any more likely than one of the Notkins still being alive.

"This is unusual enough to give me hope that there's someone who's alive and is somehow protected in the rubble and is trying to signal that they're there," Rappaport said.

Survival experts told Insider that there should be some hope that people would survive amidst the rubble but with each passing day, the likelihood of finding survivors diminishes.

"I'm always amazed at the simple things that can take life, but also the incredible things that humans can endure. So while I always hold out hope when you look at the big picture as a tactical person would have to ... really after three days, normal survival rates start to go down very quickly," survivalist Mykel Hawke told Insider.