Police on Wednesday foiled a robbery at a private gold loan company’s office in Hazra involving an insider who had hired a gang to loot a vault by sedating the staff with spiked tea.

A senior employee was arrested for allegedly masterminding the operation. He had informed the gang that the company’s manager would be on leave from Wednesday. Four robbers were also held.

The vault at the company’s SP Mukherjee Road office contained Rs 3 lakh and 13kg of gold worth over Rs 3.6 crore.

Officers said the robbery was planned for Wednesday afternoon but the mastermind was arrested minutes before the plan could be executed.

Arup Naskar, 26, worked as an assessor and was supposed to be in charge of the office from Wednesday when the manager went on leave. The police had been tipped about Naskar’s plan.

“They crushed 30 anti-allergy pills having a sedating effect and stored them in a small bottle. Naskar had planned to mix the powder in the tea served to the staff,” said joint commissioner (crime) Pallab Kanti Ghosh.

Accordingly Tapas Naskar, Kutubuddin Laskar, Aksad Gazi and Om Yadav were waiting outside for Naskar’s signal. The cops caught them before they could react.