Three people were confirmed dead and 16 were still missing early Thursday, January 26 after three office buildings, one of them 20 stories high, collapsed in downtown Rio de Janeiro, authorities said.

Officials in Brazil's second largest city said the three bodies were retrieved as rescue teams with search dogs and heavy clearing equipment sifted through the rubble.

Rio state security officials said six people were hurt, including a woman who sustained head injuries and required surgery.

Witnesses reported hearing an explosion and described scenes reminiscent of September 11, 2001, with walls of dust and debris, AFP reported.

The collapse, apparently caused by structural problems, occurred late Wednesday as Brazil races to prepare to host the 2014 World Cup and 2016 Summer Olympics, events which it hopes will highlight the country's emerging economic and political prowess.