During interrogation, the two accused confessed to the crime after they were confronted with evidence.
A woman and her friend were arrested in East Patel Nagar area for allegedly killing her husband and portraying his death as an accident, the police said. They killed the man as they thought of him as an "obstacle" in their relationship, the police added.
Anita, 30, and Arjun Mandal, 38, have been arrested, they said.
The body of 42-year-old Dayaram with injuries on his head and other parts was found lying in the shaft of a lift of an under-construction building in central Delhi's East Patel Nagar area on October 17, the police said.
According to the police, Arjun Mandal and Mr Dayaram, who were labourers, knew each other and had previously worked together. He started coming to his house and eventually had an extra-marital affair with his wife around three years ago.
"The duo considered Dayaram as an obstacle in their relationship and planned his murder to portray it as an accidental death," the police said.
A case was registered and a probe initiated, they said.
The identity of the body was confirmed by is wife, who works as a domestic help, and other relatives.
Investigations arose suspicion on Anita as she attempted to mislead the police. During call detail record analysis of mobile phones of Dayaram and his wife, one number was found to be the common link, said Deputy Commissioner of Police (Central) Mandeep Singh Randhawa.
"Dayaram had last called on the same number and even his wife had several calls with the suspected number overnight when the body of the deceased was found at the site. Even the suspected number and the mobile phones of Dayaram and his wife were at the same location between 6.30 pm to 6.40 pm on October 16," the officer said.
The user of the number was identified to be Arjun Mandal, he added.
During interrogation, Anita and Arjun Mandal confessed to the crime after they were confronted with evidence and call detail records.
"It was revealed that Anita had an extra-marital affair with Arjun for the last three years. Both were planning to eliminate Dayaram for the past few months. To execute their plan, Mandal called Dayaram at the Patel Nagar Metro Station at the instance of Anita. He invited him for drinks," the DCP said.
Arjun Mandal took him to the terrace of an under construction building in East Patel Nagar at about 7.00 pm, where they drank together. After spending almost an hour on the roof top, he pushed Mr Dayaram from the stairs of the rooftop in the shaft of an open lift hole, following which he died of injuries, he said.
To destroy the evidence, Mandal took out Mr Dayaram's mobile phone from his pocket and threw its battery in the shaft. He then went to Farid Puri and handed over the mobile phone to Anita. The accused also discarded his blood-stained slippers and clothes in Karol Bagh, the officer said.
Mr Dayaram's mobile phone, blood-stained clothes and slippers of the accused have been recovered, the police said, adding that the mobile phones of both the accused have also been seized.