The diamond broker, who had allegedly masterminded the theft of a gold necklace encrusted with 97 diamonds from a central Calcutta workshop and hid it under the floor of his house in Hooghly, is a repeat offender, police have learnt.

Two years ago, Mannan Sheikh, the diamond broker, had been arrested by Kerala police for a similar crime, a police officer said.

The police arrested Mannan on Wednesday from near the Calcutta airport.

An officer of the detective department said Mannan had been running a racket of recruiting men whom he would deploy in various workshops to steal ornaments.

“He had been arrested by Kerala police two years ago for a similar crime. He was out on bail. In his previous act, he had hired a man to steal from one of the workshops there,” said an officer.

Calcutta police have contacted the Mumbai police to check Mannan records. Photographs of the necklace have been found in Mannan’s mobile phone suggesting that he was trying to sell it to his clients across India.

Shakil Hussain, who was Mannan’s accomplice in the crime, remained untraced till Thursday evening. The police have found his mobile phone switched off.

“We are looking for him,” an officer said.

Mannan had hired Shakil and planted him in a workshop in Girish Park a month ago. Shakil, who was entrusted with setting diamonds on a gold necklace, allegedly stole the neckpiece after the diamonds were fitted. He had then handed it over to Mannan, who hid it under the floor of his house.

The necklace and the diamonds belonged to a diamond merchant who had hired the workshop for diamond fitting and polishing job. Once the necklace was stolen and one of the employees went missing, a case of criminal breach of trust by an employee and criminal conspiracy was registered with the Girish park police station.

Mannan has been booked under the same sections of the Indian Penal Code. Investigators have learned that Mannan was also engaged in trading diamonds in Gujarat.