Thousands of people are flocking to Port Dover, Ontario for a massive motorcycle event today but the OPP is warning people not to by souvenirs while they are there. 

According to police, some motorcycle gangs use the money made in selling souvenirs and paraphernalia to fund illegal activities.  

@fri13pdembedded via  

The police are warning people that by giving money to certain bike gangs, they are unwillingly supporting various criminal activities, such as drug trafficking, violence, intimidation, and even human trafficking. 

According to police, some of these bike gangs are just like other organized crime groups like mobs and street gangs and therefore just as dangerous. 

@hellsangels_mcembedded via  

They are also issuing a specific warning about buying or wearing gear from two particular bike gangs. According to OPP, the Hell's Angels and Outlaws have had increased tensions between members and anyone wearing those gangs' gear could be unknowingly putting themselves at risk. 

While police are especially concerned about those particular gangs, they do also extend that warning and say that wearing any one gang's gear could make them a target to other rival gangs. 

@outlaws_mc_officialembedded via  

The tradition in Port Dover began in 1981 when 25 friends got together on their motorcycles and decided they should do it every Friday the 13th since then. The rally has since grown, attracting thousands of people.