Superintendent of police, Seraikela-Kharswan, Indrajeet Mahatha said an FIR was registered on the basis of a statement by the victim's father but the incidence of rape could only be confirmed on receipt of the post-mortem report.
According to the FIR, the woman, who was mentally challenged for the past 20 years and was under treatment, had left home during dinner time last night and did not return.
The family members searched for her till late last night but could not trace her.
They, however, found the woman's half-naked body some distance away and informed the police before rushing her to M G M Hospital here.
Her father, however, claimed she was raped before being murdered.