Scores of security personnel behind a work-to-rule campaign at Toronto's Pearson airport have been suspended, their employer announced on Tuesday.

Garda Security Group said it had placed 74 screening officers on suspension and will take legal action against the workers after they refused to honour an injunction forcing them to return to normal service levels.

"Garda is pursuing all legal means available against the individuals responsible for the illegal work slowdown including termination of employment, contempt of court proceedings and claims for damages," the company said in a statement.

"These actions were taken following repeated notification to all employees at the airport."

The announcement comes after another apparent slowdown at Pearson airport Tuesday morning left flights cancelled and air travellers bogged in long lines.

More than a dozen flights leaving from Pearson's Terminals 1 and 3 were delayed early Tuesday morning as customers dealt with the effects of a work-to-rule campaign by security personnel.

CTV Toronto's John Musselman said lines began to thin as the morning wore on and business had returned to normal shortly before noon.

Security employees at Pearson began forcing hours-long delays last week to protest a new schedule and other working conditions.

Pearson's screeners are employees of Garda Security Group, a private company contracted by the Canadian Air Transport Security Authority.

Last week, Garda won an injunction barring workers from slowing down on the job, but travellers were still forced to deal with lineups reportedly as long as five hours on Friday.

Federal Labour Minister Lisa Raitt appointed a mediator to help come to a resolution.

Garda said on Tuesday that the majority of its 1,600 screening officers at Pearson were performing their jobs, but a small number of employees were causing the disruption and delays.

With files from CTV Toronto's John Musselman