The two people arrested on suspicion of the murder of 39-year-old Robert James Taylor remain in police custody.
Police are continuing to investigate the fatal stabbing in Lincoln which took place on Friday, April 17 in Walnut Place.
As previously reported, Robert died in hospital shortly after he was stabbed.
A man aged 42 and a woman aged 28 were arrested in connection with the stabbing.
Police have been granted extra time by magistrates to question the two suspects, on Monday, April 20.
DCI Martin Holvey, the Senior Investigating Officer in the enquiry, said: “I’m anxious for anyone who might have seen anything in the Walnut Place area between 7pm and 8pm on Friday night, and who hasn’t already spoken to us, to come forward and give us that information, but I would also like to hear from anyone who knew Robert and might have seen him on Friday so we can build up a bigger picture of his movements on that day.
“Did you see or speak to him, or hear from him, at any point on Friday? If so please get in touch with us on the non-emergency number 101, or anonymously through Crimestoppers on 0800 555 111.”