An Edmonton safety consultant says the death of a city employee in an underground sewer shaft Tuesday was most likely caused by human error.

"As a safety professional, what I'm curious about first is: Was this human error or equipment error?" said Tony Bruha, president of AJB Safety Consulting Services Ltd.

"History tells us that typically, with equipment, it's not the equipment failure. It's worker or operator failure."

A 44-year-old man died inside an underground sewer shaft on Tuesday, near the corner of Ellerslie Road and 142nd Street. Emergency crews were called to the worksite at 3:30 p.m. and declared the man dead at the scene.

He was working 20 metres below ground on a sanitary sewer tunnel, according to the city. No other information has been released about the man's identity or the cause of his death.

Bruha, who has worked with clients on similar sites, said it's unlikely the man's workplace was unsafe.

"I'd be very surprised if any safe practice or procedure was not in place. Sites like this are monitored very, very closely," he said. "There would be very little tolerance for deviation from a safe industry practice."

He also discounted a gas leak, pointing out that others on the worksite would have been affected. No other injuries have been reported by the city.

An equipment malfunction is possible, which Bruha said could make the city's contractors responsible for the incident.

"I'm not suggesting there was," he said. "But if there was a piece of equipment that was defective or broke or something and hurt the body, the prime contractor could have a major problem on their hands."

Other tunnelling worksites shut down

The city has shut down all other tunnelling sites while Occupational Health and Safety investigates the fatality site.

"Whatever they have to say about this site, they and us will determine if that applies beyond this site," said Linda Cochrane, Edmonton's city manager.

"We know so little about exactly what happened. We don't know if it's systemic across a number of sites, or if it's specific to this site."

Cochrane said other sites will reopen gradually, once they're deemed safe for workers.