Around 11:30 p.m. Sunday, just before the first floor at the Ocean Bay apartment complex began to crumble and sink, resident Elizabeth Nation told WSVN, Channel 7 she heard what she thought was “bowling balls’’ coming through the ceiling.

Furniture crashed down and the wall cracked. The first floor of the building at 8260 Byron Ave., suddenly separated from the wall, forcing the residents to evacuate. In some places, it looked as if an earthquake had hit.

Jerry Pena and his wife watched in horror as their entertainment center fell on the couch they had been sitting on just moments before.

“All of a sudden we started hearing these snaps! Boom, boom, boom!” Pena said on WSVN.

As the floor sank, the couple grabbed their baby and some diapers and ran outside.

City officials believe that water intrusion under the floor may have caused the problem. On Monday, engineers inspected the building to evaluate the damage.

At first, city officials thought five units were affected: four from the sinking floor and a fifth because of a ceiling collapse. But after further inspection, building officials declared the entire building’s 20 units unsafe.

The cause was a problem with the building’s electrical system, city officials said.

The property owner for the building, which is 1946, will be held responsible for repairs and possible relocations of residents, said Nannette Rodriguez, Miami Beach spokeswoman.

Though nobody got hurt, pictures show that in some units the damage was intense.

According to files of the Building Department, the apartment recently had some serious structural issues. Notes of violation show that just last week several water damages, holes in the wall and bug problems were reported.

Miami Herald staff writer Diana Moskovitz contributed to this report.