Units from station 3 where clearing a crash on Route 15 at South Jefferson when Ambulance 39 was alerted for injury person in the 300 block of North Market Street, so after they checked up a second Ambulance from company 2 was alerted for a second patient. Chief 3 contacted ECC on EMS 10 and was advised of a RIOT on North Market Street with unknown number of patients. Units staged at their stations and ECC advised Chief 3 that an EMS task force was being started due to a number of people injured. Chief 3 with North Market street command. After units checked on scene crews assisted Frederick Police to find out how many patients. Out of several hundred people five were taken to Frederick Memorial for treatment because of exposure to pepper spray and other minor injuries