It's an unusual case with an ironic twist that even the Ministry of Labour describes as a "very rare occurrence."

An Ontario inspector whose job it was to make sure Ottawa's light-rail transit tunnel is safe, got hurt while investigating the tunnel.

In this case, the Ministry of Labour inspector injured his leg while responding to an unrelated complaint in the LRT tunnel and has been off work for weeks, CBC News has confirmed.

Ministry officials cannot comment on the worker's injury because it's against privacy legislation, but said the incident was "non-critical," which covers injuries less serious than a broken bone.

The injury is the latest in a series of problems, both big and small, on the $2.1-billion LRT Confederation Line that include a crane toppling over, a massive sinkhole, and a wall collapsing.

Some workers have been sent to hospital with injuries, others faced close calls and told CBC they were worried for their safety.

Emergency crews rescued three workers on Nov. 10, 2016, after an industrial accident in the light-rail tunnel near the University of Ottawa. One of the workers suffered a hand injury. (Professional Paramedic Association of Ottawa)

Inspector investigating complaint

The inspector who was injured on July 5 had been called to investigate an unrelated complaint about 200 metres from the east end of Parliament Station.

Someone filed a complaint claiming there wasn't enough functioning communication equipment inside the tunnel, according to the ministry. A radio telephone system is used in the tunnel so workers can talk to one another to perform their day-to-day work, or call for help if there's an emergency, since there is no cellphone reception in the tunnel.

Oh it's a very rare occurrence, it doesn't happen all that often. - Janet Deline , Ministry of Labour spokesperson

The ministry inspector was walking along the track level of the tunnel when he tripped in a hole that wasn't visible because there was water on the ground, CBC confirmed.

Construction regulations state that a tunnel must be reasonably free of water if workers are present.

An LRT worker, who CBC is not naming because he said he fears reprisals at work, said "it's not surprising to hear" someone was injured.

"There are tons of tripping hazards and lots of water," he said. "You don't know how deep it is. People try to avoid the water by trying to walk up on the wall but it's always full of debris."

Work ordered to stop for 3 weeks in section of tunnel

The group in charge of building Ottawa's light rail system, OLRT Constructor, filled the hole after the incident, according to the ministry.

A worker took a photo of water and construction debris that was littering the tunnel floor in April 2017. At the time workers told CBC News they were worried about hazardous conditions. (Submitted) The inspector did not issue any work orders associated with his injury.

But on the same day the incident took place, the ministry issued a stop-work order interrupting construction for more than three weeks in one area of the tunnel because there was water on the ground.

OLRT Constructor was told that a 200-metre stretch of the tunnel west of Rideau Station must be "kept reasonably free of water when a worker is required to be in the tunnel."

The order was lifted after 24 days on July 27.

OLRT Constructor declined an interview about the inspector's injury or the conditions of the tunnel on July 5.

"We have no comment, other than to say that the stop-work order has been lifted," said Conrad McCallum, a communications officer with OLRT Constructor. "We are referring any inquiries about the incident to the Ministry of Labour."

2nd inspector can be called in

It is unusual for inspectors to get hurt while investigating a job site.

"Oh it's a very rare occurrence, it doesn't happen all that often," said ministry spokesperson Janet Deline.

If a ministry worker is hurt while inspecting the safety of a site, another Ontario health and safety inspector can be called in to investigate that injury. It all depends on the type of injury and if other workers are at risk.

In this case, a second inspector was not called in because the injury was considered relatively minor, said Deline.

Other problems reported

During the July 5 inspection of the tunnel, it was also reported that a cut-off rebar was protruding from the north platform level. The company complied and fixed it.

A stop-work order was also withdrawn that same day in connection to the original communications-system complaint that the injured inspector was originally called to investigate. The order was complied with and the stop-work order withdrawn.

The group in charge of construction on the LRT said 11 workers have had to take time off work due to injuries suffered on the job, a rate it said is better than the industry average.