The victim was taken to the hospital with serious injuries after a steel beam fell on the person, according to the Long Beach Fire Department.
Officials say that two others involved in the incident were treated at the scene but are doing alright.
The collapse occurred at the port at shortly after 2 p.m.
The fire department says Fire Station 20 is under construction at that location of the port and will house a fire boat, but the cause of the collapse was not immediately known.
No further details were available.
Copyright 2022, City News Service, Inc. contributed to this report