Police released a 'file photo' of the man, saying it had been 'developed' by them. The photo shows a man wearing blue shirt and black pants, similar to what was seen in the CCTV footage released by the police on Sunday.
No further details were made available.
Police are yet to crack the murder of S Swathi, who was hacked to death on Friday at the busy Nungambakkam railway station, prompting a furore by the civil society and political parties.
The Madras High Court had also come down on the state government, warning it of suo motu intervention if there was any slackness in the probe.
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The weapon believed to have been used in the murder, a sickle, had been recovered last week from the railway track near the station premises, police added.