The Uttar Pradesh's Special Task Force team on Monday arrested a key suspect in connection with the murder of celeb installation artist Hema Upadhyay and her lawyer Harish Bhambani, in Varanasi.

The police have arrested Sadhu Rajbhar, who is said to have called Upadhyay on Friday -- the day she and her lawyer were murdered. He was arrested from his house in Kavirampur village under Badagaon Police Station.

"We have arrested one person so far in connection with the double murder in Mumbai. We are interrogating him... We are questioning him for his exact role in the crime," Inspector General (IG) STF Sujit Pandey told The Times of India.

The Mumbai Police had earlier launched a search operation in Uttar Pradesh to hunt down the culprits who were believed to have fled to the state.

"A police team left for UP to trace the culprits, as it suspects that they must have fled to that state," a senior police official told PTI.

Both Upadhyay and Bhambani's bodies were recovered from a drain in Kandivali on Saturday evening, a day after they went missing. The bodies, wrapped in plastic bags, were stuffed into cardboard boxes and dumped in the drain.

A ragpicker had found the boxes and informed Laljipada Police. The police suspect that the bodies were dumped after midnight.

The hands and legs of the bodies were tied and stripped down to their undergarments. According to reports, the duo was strangulated. Their bodies were sent for post-mortem and the reports are still awaited.

Upadhyay's murder a property dispute?

Several other news reports suggested that the police are on the lookout for another suspect Gotu -- the owner of a godown where Upadhyay stored her paintings and other works. The police have detained Gotu's driver and two workers. Besides, Upadhyay's estranged husband Chintan was also questioned on Sunday.

According to a Mid-Day report, the police's suspicion on Gotu is based on a dispute between him and Upadhyay over Rs 5 lakh.

Bhambani and Upadhyay met at the latter's art studio at Laxmi Industrial Estate regarding a case on Friday evening, after which they had gone to the godown in Charkop. Their last mobile locations were traced between Charkop and Kandivali, from where their bodies were found. Both the victims' cell phones were switched off after 8:30 pm on Friday, Mid-Day reported.

The police were able to find Gotu's address with the help of the driver of the vehicle used in transporting the bodies from the godown to Kandivali. The transporter said that the men asked them to help transport "some waste material" to Kandivali.

He revealed the information to the police after reading about the murder on Saturday, as he realised that Gotu's drop location and the location from where the bodies were recovered were the same.

Meanwhile, the police have filed a case under Sections 302 (murder) 201, and 34 of the Indian Penal Code and started an investigation to nab the culprit.

Upadhyay lived in Mittal Ocean building on Juhu Tara Road in Santacruz (west) and was a well-known artist based in Mumbai. She won awards from the Gujarat Lalit Kala Academy and the national Lalit Kala Academy.

Bhambani was her lawyer since 2013 when she filed a case against her husband Chintan for alleged harassment.