A man arrested on suspicion of murdering a teenage babysitter who was stabbed to death as she looked after her young niece and nephew on Boxing Day will today face a fresh round of questioning from detectives.
It comes after a 26-year-old man held in connection with the killing of Chatherine Wynter, 19, was released without charge.
The body of the teen, also known as Katie, was discovered by her mother at 8am on December 27.
She had spent Boxing Day night at her sister's house in Borehamwood, Hertfordshire, looking after her two young relatives as a favour for her sibling who was out.
Police said the children, aged three and four, were in the house at the time of the murder but had not been injured. It is believed they could hold vital clues about the incident.
Officers arrested the 26-year-old suspect, from Islington, north London, on Tuesday in connection with the investigation but he was last night released without charge.
The 18-year-old man from Borehamwood, who was arrested on the same day remains in custody, police said.
Both were known to Wynter - and her sister - but were not direct relatives. Detective Superintendent Michael Hanlon said police would not give any further details about their relationship, but they would come out "in due course".
Specially-trained officers are expected to continue questioning Wynter's nice and nephew today, but the process is is expected to take some time because of their young age.
It is not yet know how much they saw or heard of what happened to their aunt, who regularly babysat them.
"Obviously the most important issue is the children's welfare," Hanlon said.
In a statement, Wynter's family said she was "a quiet girl who enjoyed life".
"She was a loving auntie to her niece and nephew, who she was looking after on Boxing Day," they added.
"We would ask not to be contacted by members of the media and that our privacy is respected to allow us to grieve together as a family."
Officers believe the teenager was attacked at some point between 7pm on Boxing Day and 8am on Tuesday, when they were called to the mid-terrace property in Beech Drive.
A post-mortem examination confirmed that Wynter, who also went by the surname Briscoe and lived elsewhere in Borehamwood, died as a result of stab injuries.
Hanlon said no weapon has been found but a number of searches were taking place.
He said: "Firstly, our thoughts are with the victim's family.
"As you can imagine, this is an extremely traumatic time and they are being supported by specialist family liaison officers.
"We have a team of detectives currently working on the case who are looking at a number of lines of inquiry to establish exactly what happened. However, I would like to appeal to the communities of Borehamwood to help us."
Police are investigating whether there were any signs of a break-in at the house where Wynter was found, but said she and the children were the only people staying there on the night.
Floral tributes were left near the scene. One read: "To darling Katy. RIP angel. We will miss you so much."
Neighbours described the death as a "tragedy".
It is not known where Wynter's sister went on Monday night, but police said she was staying locally.