The brand-new pedestrian bridge has collapsed onto a highway. MIAMI — A pedestrian bridge that was under construction collapsed onto a busy Miami highway Thursday, crushing at least eight vehicles under massive slabs of concrete and steel and killing multiple people, authorities said.The Miami-Dade County fire chief says four people have been found dead in the rubble.Search-and-rescue crews drilled holes into the debris and used dogs to look for survivors. They had to work carefully because part of the structure was still unsafe.Fire Chief Dave Downey said at a news briefing Thursday evening that four deceased people had been found at the scene by first responders. He also says nine victims were removed “early on” and taken to hospitals. But he did not elaborate on their conditions.He says “search and rescue mode” is continuing after nightfall.The 950-ton bridge had been assembled by the side of the highway and moved into place Saturday to great fanfare. The span stretched almost 200 feet to connect Florida International University with the city of Sweetwater. It was expected to open to foot traffic next year.“We have a national tragedy on our hands,” Sweetwater Mayor Orlando Lopez said.Jacob Miller, a senior at FIU, was visiting a friend in a dorm when he heard sirens and horns honking. He went to a balcony and could see rubble coming down.