What to Know About the Building Collapse in Surfside, Fla.

Firefighters, search dogs and emergency crews scoured rubble for survivors of a residential building that partially collapsed just north of Miami Beach on Thursday morning.

At least one person was killed, the police said, and dozens of others remained unaccounted for at the scene in Surfside, Fla.

What happened?

About half of the units in the 12-story tower had collapsed, according to Daniella Levine Cava, the mayor of Miami-Dade County, Fla.

The beachside building, at 8777 Collins Avenue, is called Champlain Towers South and was built in 1981, according to city property records. There were about 136 units in the building, according to the mayor.

Fiorella Terenzi, an associate professor at Florida International University who lives in a neighboring building, Champlain Towers East, said she woke up early Thursday to a loud noise.

The sound “was like a big thump all of a sudden,” she said. At first she thought it was thunder but then started to hear sirens. When she left the building, dust was everywhere.

“I could see that half of the building of the Champlain Towers South was collapsed like a sandwich,” said Ms. Terenzi.