PHUKET: Police used Facebook to bust a gang of underage racers who were turning Phuket's bypass road into a speedway for modified motocycles early today.

Twenty-one youths and a girl all under 18 - the youngest just 15 - were netted when about 50 police and volunteers raided the ''hot spot'' near the Outlet retail centre soon after midnight.

''When vehicles are stopped from turning right at the bypass road intersection with Thepkasattri Road, the racers burned along the bypass road,'' an officer from Phuket City Police Station told Phuketwan today.

''Then they race back - on the wrong side of the road.''

The racing using modified motorcycles had been taking place at different venues around Phuket for three years, according to police.

''One of them let slip on Facebook where Friday night's events were being held so we were ready for them this time,'' the officer said.

A total of 28 motorcycles were confiscated.

Officers will continue interviewing the arrested youths at Phuket City Police Station today with parents being invited to turn up to collect their children. All were also tested for drugs.