Rescue workers combed through the rubble of a pedestrian bridge that collapsed onto several lanes of traffic at Florida International University, but hopes of finding more survivors were fading early on Friday, police said.

Six people were confirmed dead after the newly built 950-ton bridge crushed vehicles on one of the busiest roads in South Florida on Thursday.

"Unfortunately, this has turned from a rescue to a recovery operation," a Miami-Dade police spokesman said on Friday morning. The number of dead could rise as more vehicles could still be under the concrete and twisted metal, he added.