A man and two of his aides have been arrested for the murder of a woman and her three children whose bodies were recovered in sugarcane fields with their throats slit in the Fakharpur area of Uttar Pradesh's Bahraich district on September 11.
The 35-year-old victim was a resident of Thane in Maharashtra.
The state government had announced Rs 1 lakh cash prize to the team which worked out the case within a week.
The accused men, who were arrested on Saturday, have been identified as Nanku and his aides, Salman Khan and Danish Khan.
Nanku is the main culprit in the case while Salman and Danish helped him in executing the crime for money. The police have recovered three mobile phones, the woman's phone and a knife.
Superintendent of Police (SP), Bahraich, Sujata Singh, who led the probe, said Nanku of Bahraich worked at a small eatery in Thane.
"Nanku came in touch with a woman, a divorcee, who also used to work in the eatery with her three children (aged 4, 7 and 11 years)," said Singh.
She said Nanku, who was already married, lied to the woman that he was single and befriended her.
"The woman, who wanted to marry Nanku to support her children, fell into his trap," the SP said.
The woman asked Nanku to run his own business in Thane.
When Nanku said he had no money, she sold her small house to help him," the SP said.
After getting money, Nanku thought of getting rid of the woman and her children.
"Nanku asked her to accompany him to his house in Bahraich when she insisted on marriage. They reached Lucknow via train on September 9 and then to Bahraich by road. Nanku called his aides who helped him execute the crime.
They dumped the bodies at two different places to mislead the police," the officer said.
Police had first recovered the bodies of two children on September 11 and then of a woman and a child on September 12.