Police said the sketch was prepared based on the inputs provided by two persons who claimed to have seen a person at the time of the crime on April 28 in the neighbourhood of the victim's wayside home in Perumbavoor.
It is not clear whether the persons currently under the custody of police have similarity to the sketch of the person.
Amid widespread protests over the delay in arresting the culprits behind the brutal murder committed nearly a week ago, police remained tight-lipped about the ongoing probe carried out under the direct watch of top officials.
The police, facing flak for alleged lapses in the initial investigation into the incident, continued to grill the person picked up from Kannur.
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He reportedly had left the area soon after the incident and it was found from the examination of mobile phone records.
The woman, who hailed from a poor family, was allegedly subjected to rape and brutal assault using sharp edged weapons before being murdered at her house.
No arrest has been made so far in the crime that shocked the state triggering, intense politicking ahead of the May 16 Assembly elections.