The youth and his friend had been picked up for questioning when they were talking to a girl yesterday afternoon, relatives said.
They were allegedly beaten up and questioned in connection with gold chain thefts in the area.
Police maintained that the duo were picked up as they did not have relevant papers for the motorbike they had.
Vinayakan, who works in a beauty parlour, was also asked to shave off his long hair.
Thrissur Police commissioner, T Narayanan, told PTI that Guruvayur Assistant commissioner of police has been asked to probe into the incident.
Asked if the teenager had been tortured by police, the Commisisoner said only a probe would bring out the truth.
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