Two other workers involved in constructing the tunnel were rescued earlier in the day, the official state-run Xinhua news agency reported.
The cause of the accident was not known, but rescuers noted the collapse occurred in a section of the tunnel where two sewage pipelines were located.
The rescue attempt was continuing.
Couple calls 9-1-1 over missing hash browns; assault McDonanld's employees
Workers accuse National Zoo of animal mismanagement