Over 15 motorcycles were set ablaze by unidentified persons at three different spots in the city on Monday morning. The Samta Nagar police received a call around 2.30 am from a resident of Hanuman Nagar,who said 10 motorcycles were set on fire outside his residence. Within half an hour,the police received calls about motorcycles being burnt in two other areas. Since December,the city has witnessed seven incidents of torching vehicles. The reason behind most of the cases was personal rivalries,the police said. Anant Kenjele,senior inspector of Samta Nagar police station,said a case has been registered against unknown persons and they are in the process of finding out the motive behind the act. The bikes were owned by residents of the area and were parked in front of shops at Hanuman Nagar,metres away from the police station. Vijay S,who had parked his motorcycle outside his house,got up after seeing the flames coming out from the parking lot. The fire spread to his house and injured his father. My 80-year-old father,who is keeping unwell,was caught in flames. We somehow rescued him and took him to the hospital, said Vijay,who owns a store in Kandivili. I usually park my motorcycle in the compound,but since my father was unwell,I had parked it outside the house for emergency, he added. The police said they will contact the police stations of areas where vehicles have been burnt in the past to verify the involvement of any gang in the incidents. Most of the incidents in Sion,Byculla and Vikhroli have been a result of personal rivalry,but we will check to see whether any gang is operating in the city, said Kenjele. Sanjay Patel,another resident whose bike was set ablaze,said,I used to park my bike outside a shop and pay Rs 200 every month. I do not even have an insurance and cannot afford another motorcycle.