LOS ANGELES -- A portion of a parking garage being built to house buses in downtown Los Angeles collapsed on Friday, just minutes after nearly 200 construction workers were alerted that something was wrong and fled to safety, officials said.
A section of the structure measuring about 50 by 75 feet came crashing down just before 9 a.m. in the heavily congested area.
Minutes earlier, 180 people had been working on the structure, said Metropolitan Transportation Authority spokesman Marc Littman.
"Workers were pouring concrete in the upper parking deck of the northeast corner of the building," Littman said. "During construction we had pour watchers from below notice something was amiss. They immediately alerted workers to clear the area."
A few minutes later, the structure's second story, where 10 people had been working, collapsed onto the first level.
A Los Angeles Fire Department search and rescue team found no one trapped amid the rubble.
"Fortunately we have heard that all workers have been accounted for," Fire Department spokesman Erik Scott said.
Littman said construction was halted while investigators try to determine what caused the collapse.
"No work will be resumed until a thorough investigation is conducted by Metro, the contractor and the design firm," he said.
He noted that concrete had previously been poured without any problems as several other sections of the sprawling structure were built.
Traffic was briefly snarled when the building fell.
The garage is part of a complex that will include a bus yard housing as many as 200 transit vehicles. It will also accommodate 500 employees.
"This is where you store buses, work on buses, clean buses and dispatch buses to various locations," Littman said.
The construction site is adjacent to the west side of the Los Angeles River, near county jails and a transit plaza.
The project, which stretches across three blocks, has been under construction since 2012. It's due to be completed in January.