Tirupati: Three vehicles were gutted in a freak fire incident near Balapalli checkpost along the Kadapa-Tirupati highway on NH-716 close to Railway Kodur on Tuesday.According to information, a truck heading from Kadapa towards Tirupati met with a breakdown at around 8.30 am. The driver of the truck parked the vehicle on the roadside and went in search of a mechanic. Moments later, a speeding SUV heading towards Tirupati from Kadapa rammed into the stationary truck from behind at high speed. Four inmates in the car sustained injuries and were rushed to the govt hospital at Railway Kodur.In the meantime, at around 11.30 am, another car heading towards Tirupati from Kadapa stopped at the same spot when its driver noticed smoke coming from the engine. While what happened after that remains a mystery and is being investigated, the car suddenly got engulfed in fire, which then spread to the SUV and the truck that were involved in the morning accident.Commuters passing along the stretch noticed the three vehicles going up in flames and alerted local police, who rushed there along with fire tenders and contained the fire. No casualties were reported in the incident.