The arrested persons included the main accused who had been engaged as a water carrier to the residence of the sisters at Hindustan Park in Gariahat police station limits for over 6 years, a senior Kolkata Police officer said.
The dacoity took place in the morning after the water carrier left the house.
"We detained the person who had been working as a water-carrier to the house for more than six years suspecting him to be an accused. After questioning him, we found that he was involved in it along with five others," she said.
"After he (the water-carrier) left, there was a knock on the door. When we opened the door, five masked men barged into the room and tied both of us," Mohua Ghosh, one of the two sisters said.
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"They were holding knives. They took out all the jewelleries and cash from the almirahs. It seemed they had information where we keep our valuables," Rita Ghosh, the other sister, said.
"We have recovered some of the stolen jewelleries and the cash. We are questioning the arrested men and trying to spot the sixth person who is absconding," she stated.
Crime against elderly people in the city has been growing in recent times.