“The boy might have been poisoned. Preliminary investigation suggests the family was under severe debt. The suicide note mentions certain names and we are inquiring whether they have any connection with the incident,” said Pravin Kumar, Superintendent of Police, South 24 Parganas.

The incident came to light when neighbours visited the family around 8 am, but received no response after repeated knocks at the door. They broke open the door to find them dead.

Jayanta Kar Roy, a neighbour, said: “Rahul was lying on the bed, frothing at the mouth. He might have been poisoned first by the couple before they committed suicide. The couple was found hanging in the two separate rooms.”

Aloke Dutta, one of his friends, said that Dipankar, a contractor, had taken a loan of more than Rs 60 lakh from several businessmen. But he could not pay them back as he failed to recover the money from a contractor. “He had supplied a huge quantity of cement to the government contractor but did not receive the payment,” Dutta said.