At least 11 people are dead and 150 others remain unaccounted for after a 12-story residential building partially collapsed in South Florida's Miami-Dade County last week, officials said.

A massive search and rescue operation entered its sixth day on Tuesday, as crews continued to carefully comb through the pancaked pile of debris in hopes of finding survivors.

The partial collapse occurred at around 1:15 a.m. local time last Thursday at the Champlain Towers South condominium in the small, beachside town of Surfside, about 6 miles north of Miami Beach. Approximately 55 of the oceanfront complex's 136 units were destroyed, according to Miami-Dade Fire Rescue Assistant Chief Raide Jadallah.

So far, 136 people who were living or staying in the condominium at the time of the disaster have been accounted for, according to Miami-Dade County Mayor Daniella Levine Cava, who noted that the numbers are "very fluid" and "will continue to change."