Two telecommunication workers died Thursday after a workplace accident in a sewer tunnel in Oakville.

The two men lost consciousness in the sewage system while working on some wiring. When emergency crews pulled them to the surface with ropes and a basket around 11 a.m., they had no vital signs and couldn't be resuscitated.

Both were taken to Oakville Trafalgar hospital, where they were pronounced dead. Their identities were not immediately released, pending notification of next of kin.

The accident happened at in the area of Third Line and North Service Road, just north of the Queen Elizabeth Way.

Halton police Sgt. Peter Payne said it's not clear what happened but added that the air quality in the maintenance tunnel was too poor for investigators to enter.

Air quality tests were being conducted Thursday afternoon. Payne said autopsies will be scheduled as well.