Jahangir Gulamov, head of the rescue effort, said: "We have have been working non-stop for three days and will continue."
"But after so much time, the chances of finding people alive are very slim."
Building safety violations were the most likely cause of the accident and four representatives of the construction company working on the building have been arrested, officials said.
Ilham Aliyev, the Azerbaijani president has ordered an investigation.
Baku is in the midst of a construction boom and high-rise buildings are cropping up across the city as energy-rich Azerbaijan enjoys record economic growth from surging oil and gas exports.