A memorial to Ontario firefighters who died in the line of duty has been desecrated with anti-government graffiti.

Authorities say the messages were spray-painted on the monuments at some point Monday night. 

Pedestrians walking by the memorial, located just south of Queen's Park, saw a large black glob of paint covering the names of fallen firefighters. Other sections of the tribute had messages that said "Firefighters 4 McGuinty," "Guns bad" and "Dalton gang."

Ontario Premier Dalton McGuinty called the act "cowardly."

"It's cowardly and despicable," he told reporters Tuesday morning. "That's a memorial that pays tribute to people who have gone rushing in when the rest of us rushed out and they lost their lives as a result of their service to us.

"We'll work with the firefighters and do whatever we need to do to help clean it up right away," he continued.

Crews who began cleaning the graffiti on Tuesday believe they will be able to remove all of the paint.

The head of the provincial firefighters' association was also upset by the vandalism. He was at the site Tuesday to assess the damage with the designer of the monument.

Authorities say they are reviewing security cameras in the area and are looking for a male suspect who was spotted at the monument at about 9 p.m. on Monday.

There is speculation the monument was vandalized because McGuinty promised the firefighters' association extra health and disability benefits during the last election.

With a report from CTV Toronto's Paul Bliss