An assistant sub-inspector on Tuesday became the first “insider” to be arrested on charges of playing a role in the constable recruitment scam in Calcutta police.

The deputy commissioner of police (detective department), Jawed Shamim, said Nanda Kumar Pal had been posted in the Central Reserve Office and given the task of verifying whether those who had reported for police training were actually those who took the recruitment test in January.

“He allowed some of them to join the Police Training School despite knowing that dummy candidates had represented them in the test. The photographs in the official records were those of the dummy candidates and not of the recruits standing before him,” Shamim said.

Pal confessed to his involvement in the scam after several hours of interrogation at Lalbazar, beginning Monday.

Six of those who got jobs without taking the test have been arrested so far. Three more persons — a photographer, a dummy candidate and the owner of a training centre — are in custody, too. The masterminds of the scam, former constables Gopal Das and Bappa, are on the run.

Pal, a resident of Usthi in South 24-Parganas, was produced in court after his confession and remanded in police custody till May 18. The assistant sub-inspector was on deputation to the Central Reserve Office for five years.

Pal had no idea that he was under investigation until officers summoned him for interrogation. “He came to the Central Reserve Office on Monday and was taken aback when we called him to the anti-fraud unit around 2pm. His answers were not satisfactory and we decided to arrest him,” one of the investigators said.