A boy and a girl, both teenage minors, who “met” through a social media platform, were detained on Monday for the alleged murder of the girl’s mother three weeks ago.

The woman’s death at her home on the southern fringes of the city three weeks ago did not raise any suspicion and was passed off as a natural death.

However, on Sunday, the girl’s father said his daughter and her friend had killed his wife on June 6 to avenge her objection to their friendship.

Police on Monday detained both children. A murder case has been registered at Thakurpukur police station.

The deputy commissioner (southwest division) of Kolkata Police, Rahul De, said the girl’s father went to the police station on Monday and made the allegation about the involvement of his daughter and her friend in his wife’s death.

“Based on his statement, the minors have been detained. They will be produced before the Juvenile Justice Board on Tuesday,” De said.

An officer at the police station said the girl’s father on Monday told the police that his daughter and her friend had killed his wife and threatened to falsely implicate him in the murder if he spilled the beans.

“According to the father’s statement, the girl invited the boy to their house on the night of the incident. The boy smothered the woman acting on the instructions of the girl and then threatened to kill him if he dared to raise his voice,” the officer said.

The father was allegedly made to call a doctor and present his wife’s death as a “normal death”.

The police said a local doctor visited the house the next morning and issued a death certificate, following which the body was cremated.

Officers said the doctor would be questioned as his statements would be crucial to the investigation.

It was only on Sunday that the father divulged the “truth” to some neighbours after being allegedly threatened to be killed if he did not pay the young boy and girl ₹50,000. He went to the police on Monday.

The police said that though the body had been cremated without a post-mortem, a murder case has been started based on the statement of the woman’s husband.