WILLITS, Calif. (KGO) -- A serious collapse happened Thursday afternoon on the embattled Caltrans freeway project in Willits.
Four construction workers were injured and one was trapped beneath the debris for a while.
Caltrans is building a freeway bypass around the town of Willits in Mendocino County.
Officials say workers were pouring concrete, when a 150-foot temporary steel and wooden structure known as falsework suddenly collapsed.
There's word yet on the injured workers'conditions.
The collapse did not happen in an area accessible to the public.
The 5.9-mile overpass has been beset by lengthy delays and cost overruns. The $210-million project is 50 percent complete and already two years behind schedule.
Lawsuits and protests by opponents who say the project is unnecessary and damaging to the environment have contributed to the delay.
State occupational safety investigators are expected to visit the site on Friday.