Five people working on the future Airport station that's part of the Stage 2 south extension of the Trillium Line were injured Thursday morning, the general manager for OC Transpo says.

Four of the five injured workers were taken to hospital and one was treated at the scene, said John Manconi in a memo.

Among the four taken to hospital, one has a potential spinal injury and another has a potential head and chest injury which is serious but not life-threatening, the Ottawa Paramedic Service said. No information was available about the two other hospitalized workers.

The incident happened just before 10:30 a.m.

Ontario's Ministry of Labour said the injured men work for Man Steel.

SNC-Lavalin, the contractor building the Trillium Line extension under the name TransitNext, said the workers were hurt at the loading dock for the Ottawa International Airport, the site of the future transit station.

The current work involves building caissons, "deep cylindrical shafts drilled into the ground" that will provide support for the station, said Mandy Downes, a spokesperson for SNC-Lavalin.

"Today, crews were assembling the rebar cages that get lowered into the drilled caisson. We are not yet certain of the cause, but the rebar cage collapsed on the five workers that were assembling it from the inside," Downes said.

Ottawa police, the province's Ministry of Labour and TransitNext were on scene Thursday, investigating the work site.

SNC-Lavalin said the ministry has halted the rebar assembly work involving the caissons, but the company has clearance to continue other work at the airport.

The Trillium Line O-Train is expected to be offline for the next two years to allow for the construction of a $1.6-billion, 16-kilometre extension to the south, which includes the train link to the airport.