Ottawa police are investigating reports of taxi vandalism by protesters who shut down the Airport Parkway twice on Tuesday.

A video posted to YouTube showed protesters smashing the back windshield of a Blueline Taxi, while multiple taxis sitting at the dispatcher's headquarters also featured windshield damage.

"Evidence has been and continues to be gathered and charges will be laid if warranted," according to an Ottawa police news release.

Dozens of airport taxi drivers blocked traffic along the Airport Parkway on Tuesday morning in an ongoing labour dispute. (Laurie Fagan/CBC) The Airport Parkway reopened just before 6 p.m. Tuesday after a second sit-in protest by frustrated Airport Taxi drivers and their supporters.

The protests come during the fifth week of an ongoing labour dispute between the drivers and their dispatcher, Coventry Connections.

Dozens of drivers walked along both lanes of the parkway and then sat down on the road, halting traffic. Traffic was rerouted.

Police were called to the scene and watched over the protest, saying the drivers have the right to gather and demonstrate peacefully.

Multiple taxis vandalized

The peace seemed to end on Tuesday afternoon as protesters were caught on a dashboard camera smashing the back windshield of a Blueline Taxi.

"[The] dispute escalated into violent actions by striking drivers against the Blueline and Capital drivers who have been fulfilling the contract," the Ottawa Airport Authority said in a news release Tuesday, adding this has affected some of its customers.

These Blueline taxis were allegedly vandalized as they tried to drive by protesters on the Airport Parkway on Sept. 8, 2015. (Steve Fischer/CBC) "We do not condone any kind of violent behaviour … and we must be able to maintain normal airport operations. We call on our partners at the Ottawa Police Service to maintain the peace."

Airport taxi drivers are currently locked out of the airport taxi stand in an ongoing labour dispute with Coventry Connections over an increase in the fees Coventry is charging drivers for the right to pick up airport fares.

Ottawa police said if you have information regarding the taxi protest violence, call police at 613-236-1222, ext. 3566.