An Ottawa union leader says workers had expressed concerns about ice on the walls of a construction pit where a worker was killed by falling ice Wednesday morning.

The 25-year-old man was critically injured after a mass of ice about 12 metres long slid off the wall of the Claridge Icon condominium construction pit at 505 Preston St. around 7:15 a.m., according to paramedic Supt. Darryl Wilton. The chunk that struck the worker weighed between 20 and 45 kilograms, Wilton said.

Ottawa rescue fire construction pit Preston Street March 23 2016

Emergency crews got the worker onto a backboard to lift him out of the pit. (Scott Stilborn/Ottawa Fire Services)

Paramedics and firefighters got down to the bottom of the pit using a long set of stairs. The man was able to speak when they first reached him, but he eventually slipped out of consciousness, Wilton said.

The other construction workers on site helped secure the scene for emergency crews, Wilton said.

"The construction crews were amazing," he said. "They actually moved a Employer backhoe that was in the bottom of the trench, and they moved the bucket of the backhoe over to create a shield, so that if any further ice fell that would create a shield between the emergency workers and the wall."

Another construction worker used a crane to lower a backboard to the man and then hoist him out.

The man lost vital signs as he was being lifted out of the pit, Wilton said. The firefighter who was with him performed CPR as they ascended.

He was lifted out at about 7:45 a.m. in critical condition and was taken to hospital, where he later died. His identity has not been released.

Ontario's Ministry of Labour is investigating with assistance from Ottawa police.

Concerns raised, union claims

The head of a group representing nearly 100 Ottawa-area unions said the death was preventable.

Sean McKenny Ottawa District Labour Council

Sean McKenny is president of the Ottawa & District Labour Council, which represents nearly 100 unions in the Ottawa area. (CBC)

"That sheet of ice … could have been removed [prior to today]. It wasn't. All those workers that were working in the pit were subjected to working in an unsafe environment for sure," said Sean McKenny, president of the Ottawa & District Labour Council.

"Our understanding is that it had been pointed out to several people ... on several occasions that the ice looked like it could fall but there were no precautions, at least as we understand it, taken to ensure that the ice was removed."

A nearby resident who didn't want their name used took a photograph of the ice being removed in February.

Ice Claridge Icon Preston Carling Construction

Workers remove large pieces of ice from the wall of the Claridge Icon condominium site on Preston Street in February. (Submitted to CBC News)

McKenny said he will push for Ottawa police to conduct a criminal investigation into the fatality.

Claridge declined to comment when contacted by CBC News.

The Ministry of Labour said it won't be able to provide information about the province's regulations concerning dangerous ice at work sites until Thursday.

Icon tower construction critical

Paramedics say a large piece of ice fell from the wall of the condo construction pit, critically injuring the worker below. (Giacomo Panico/CBC)