Indrajit Saha’s first birthday turned out to be his last.

Police said the year-old baby, whose body was found in a shopping bag beside a Ultadanga canal on Sunday, was killed on his first birthday by family elders engaged in a property dispute.

The child’s mother, Bula, 30, went missing hours before the body was found.

“We fear she, too, has been killed. We searched their Beleghata house but found no clues,” said an investigating officer.

Indrajit was murdered early on Sunday. “We suspect the 67-year-old paternal grandmother Arati, 38-year-old uncle Satya and his wife Nandita,” said A.K Lahiri, the officer-in-charge of Ultadanga police station.

Arati and Nandita have been detained but Satya, the younger brother of Indrajit’s father Bidyut, is absconding.

“The murder seems to be the fallout of a property dispute between Bidyut, a vegetable seller in Sealdah, and Satya,” Lahiri said.

The post-mortem report suggests the child died of head injuries. But cops suspect Indrajit was gagged to death before being hit on the head.

Sleuths, as well as neighbours, said Bidyut and Satya had been fighting over the respective shares of their ancestral house in Beleghata and some other family property since the death of their father a few years ago.

“Arati used to support Satya, who works in a soft drinks factory in Dankuni, as he is better off than his elder brother,” an officer of Ultadanga police station said.

Shyamali Koley, a neighbour of the Sahas, said: “I heard Satya and his wife quarrelling with Bula early on Sunday. But we never thought that the couple, along with Arati, could kill the child.”

Another neighbour said: “Satya often beat up Bidyut and Bula and threatened to kill them if they did not vacate the house.”

The baby boy’s body was discovered on Sunday after Ultadanga residents spotted two legs sticking out of an abandoned shopping bag. The boy, face covered with a gamchha, was wearing a sweater. Two pendants were attached to a chain around his neck.

“On Monday morning, a woman called up Beleghata police station and alerted the duty officer about the child’s identity,” said an officer.

A shattered Bidyut, who identified his son’s body at the morgue of RG Kar Medical College and Hospital later on Monday, said: “They have killed my son and wife. I am finished.”