A post-mortem is expected to be carried out on Tuesday on the body of the 21-year-old man who died in hospital after being stabbed shortly before 1am on Saturday.

No one has been charged in relation to his death, and the police strike force investigating the killing has widened as more officers hit the ground in Tamworth.

On Monday, detectives spent a third day interviewing witnesses for clues as to what happened inside the Green Street home between 11pm on Friday, and when the first Triple Zero call was made just before 1am.

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"People are still being interviewed by detectives and inquiries by Strike Force Mindoro are continuing," Oxley Detective Acting Inspector Jason Darcy told the Leader on Monday.

Investigators are remaining tight-lipped on the man's injuries, and the nature of the deadly stabbing, including who was inside the home at the time.

"A post-mortem will be carried out to determine the man's death," Detective Darcy said.

"We're still appealing for any witnesses to come forward, particularly anyone in the Green Street area on Friday night.

"Whether they were at a house party or coming and going - anyone that might have seen or heard anything - we would urge them to come forward and speak to detectives."

Strike Force Mindoro - the dedicated police operation launched in the wake of the man's death - has interviewed more than a dozen witnesses who are believed to be family and friends of the man, as well as those in the Green Street area.

On Monday, more investigators arrived in Tamworth from across the Western Region. It's in addition to the New England team of police who were deployed on Saturday to back Oxley detectives who are leading the police probe.

One woman - a 26-year-old who is believed to be related - was arrested in the early hours of Saturday morning and taken in for questioning. She was released that day.

No charges have been laid, but the house party on Friday night in Green Street is key to the investigation.

Uniformed officers are maintaining a crime scene guard on the home in Green Street - the third day in a row that has seen investigators coming and going from the scene of the deadly stabbing.

Investigations are continuing and anyone with information, or who has dashcam or phone footage of the area on Friday night, is being urged to contact Tamworth police on 6768 2999.