Officials say a "very deep fire" is hampering rescue efforts at a collapsed oceanfront condominium near Miami, where authorities are racing to recover more victims beneath the rubble. Miami-Dade Mayor Daniella Levine Cava says rescuers are using infrared technology, water and foam to battle the blaze, whose source is unclear. Smoke has been the biggest barrier. One hundred fifty-nine people remain unaccounted for since the collapse on Thursday. At least four were killed. ------------------ For More News and Videos SUBSCRIBE and Turn Notifications On https://bit.ly/2r0BEND Get a Digital Subscription to the Tampa Bay Times https://bit.ly/2Xinunj Follow us: Facebook ► https://www.facebook.com/tampabaycom Twitter ► https://twitter.com/TB_Times Instagram ► https://www.instagram.com/tampabaytimes ------------------ #miami #surfside #surfsidecondo