Two construction workers died Thursday after a workplace accident in Oakville.

Two men were pulled from a sewer with no vital signs at a site on Third Line and North Service Road, just north of the Queen Elizabeth Way, just before 11 a.m., CTV's Jim Junkin reported.

Emergency crews tried to reach the men in the sewer and bring them to the surface. The victims were airlifted to Oakville Trafalgar Memorial Hospital, where they were later pronounced dead.

Police and emergency workers are not yet sure what happened to the workers, who were 33 years old and 52 years old, in the sewer.

Police said sensors had been deployed to check for abnormal readings in the sewer. Results showed the air quality levels were very poor, Junkin reported.

It's not clear if the victims were working on a new sewer project or an existing one, but the two men had been working for the company for 15 years and 32 years respectively, and were considered pros. Other workers at the scene were badly shaken by the tragic accident, Junkin reported.

All work on the project has been halted as a result, and inspectors from the provincial labour ministry have been called to the scene to investigate the circumstances behind the accident.

No names have been released.

With a report from CTV's Jim Junkin