There are 2 things you can do. The first is what Wlanman said as to find out what application is running multicast. Usually in a Layer 2 network multicast frames will transmit on all ports unless the switch has IGMP snooping.
First you have to decide if you need that multicast application or not. If you don't, then what I suggest is to create a filter first on the controller to filter out the multicast. You can use a sniffer like wireshark or wildpackets to sniff the air and find out the multicast address. Or you can filter out multicast from the mac level by filter out any traffic destined to dest mac 01:00:5e.
If you do need the application running multicast then I would suggest limiting the rate of multicast to something lower than 50pps.