Video from the scene shows a side of the building -- more than 10 stories tall -- having fallen, with huge piles of rubble underneath and a large number of first responders.
One person there has died, and at least 10 others were treated on the scene, Surfside Mayor Charles W. Burkett said.
"This is a horrific catastrophe. In the United States, buildings just don't fall down," Burkett said.
Rescue teams scrambled to the scene -- 8777 Collins Avenue -- a few miles north of Miami Beach. More than 80 rescue units responded, MIami-Dade Fire Rescue said.
Kimberly Morales told CNN she lives in the building across the street from the collapse and was awakened by building alarms going off and pounding on her door.
"I woke everyone up in the room because when I looked out the window, I saw everyone outside," she told CNN. "I told everyone to hurry up and leave the building."
Morales said she didn't hear the building collapse but when she went outside, she saw a significant portion of the building was missing.
She's now in a community center with other evacuees, she said.
The building was undergoing roof work, but it's unknown whether this was a factor in the collapse, the mayor said.
This is a developing story and will be updated.