The arrested construction workers have been identified as Uttam Mandal (24) and Ram Mandal (21) of Malda district in West Bengal, police said.
"The accused have confessed to their involvement in the crime. The accused further confessed that they sexually assaulted the victim and took away her mobile phone and credit card", a CB-CID official involved in the investigations told PTI.
Police said the arrested would be produced before a local court tomorrow.
The decomposed body of Uma Maheswari, who was working with Tata Consultancy Services, was found at Siruseri near here on February 22.
Uma Maheshwari had gone missing on February 13 and her father had filed a case of missing with the police who had not taken the matter seriously.
Following the discovery of the girl's body which bore stab injuries, the police suspended the Kancheepuram police station Police Inspector.
As the case evoked criticism over safety of women employees working with IT firms in the wake of the gruesome murder, the state government transferred the case to CB-CID wing for investigation and the police had announced Rs two lakh reward to those who provide information on Uma Maheswari's killers.
Uma was a native of Salem district and living in Medavakkam here.