A 24-year-old woman and her minor son were found dead, allegedly killed over dowry, in East Champaran district early on Tuesday morning.

Pradeep Sah, a resident of Areraj in East Champaran district, around 145km northwest of Patna, has lodged a complaint accusing the in-laws of his sister Prity Devi of killing her and her son Aryan. They were killed around Monday midnight when they were sleeping at their house in Rajepur village under Govindganj police station.

Areraj sub-divisional police officer Nurul Haq said the bodies were recovered from the room around 6am with injury marks around their necks.

Pradeep lodged a complaint with Govindganj police station on Tuesday alleging that his sister, married in 2013, had been killed for dowry.

He told the police: "Her in-laws were demanding Rs 2 lakh as dowry, which we were not in a condition to pay. This led to the murder of my sister and her minor son. The mother and son were strangled to death on Monday night. Prity was being harassed for dowry since her marriage in 2013."

Govindganj police station house officer Rajiv Kumar said one suspect - Prity's sister-in-law Sunita Devi - has been detained for interrogation while raids are on to nab the accused. "The woman's husband is abroad," Rajiv told The Telegraph over phone.

Prity married Nirmal Sah in 2013 during which her family offered the in-laws a large amount of gold ornaments and other valuables besides cash. Nirmal left for the UAE soon after the wedding. Pradeep said in Nirmal's absence, his family members - Prity's mother in-law, sister in-law and father-in-law - harassed her and pressured her for more dowry. "When we expressed our inability to pay the money, the in-laws killed her," Pradeep said in the complaint.

Prity had recently gone back home in Areraj where her in-laws reached on Saturday, asking her father Hridaya Sah to allow Prity to go with them.

On Tuesday, Prity's father reached Rajepur to find his daughter and grandson murdered. Govindganj police station house officer Rajiv Kumar said Prity's in-laws have been booked under sections 304(B) and 34 of the Indian Penal Code.

This is the second alleged dowry death in the state since chief minister Nitish Kumar launched his war on dowry and child marriage last Monday. Last week, a JDU leader in Muzaffarpur and his family were accused of killing his daughter-in-law for dowry and tampering with evidence.