A judge has given police permission to continue quizzing an 18-year-old man arrested in connection with the Boxing Day murder of teenage babysitter Katie Wynter.
Forensics teams are still working at the scene.
Nineteen-year-old art student Wynter was stabbed to death while she babysat her four-year-old niece and three-year-old nephew
It is not known if the children she was looking after witnessed the brutal attack at the address in Beech Drive, Borehamwood in Hertfordshire.
Two men were arrested in connection with the incident.
One was a 26-year-old from Islington, north London, the other an 18-year-old from Borehamwood. Both were known to Wynter, said police.
The Islington man has been released with no further action, while the courts granted police permission continue to hold the 18-year-old until the evening of 30 December.
Wynter's body was discovered by a family member, thought to be her mother, on Tuesday morning.
"Katie was a quiet girl who enjoyed life. She was a loving auntie to her niece and nephew," said a tribute from her family.
Detective Superintendent Mick Hanlon of Hertfordshire Police, who is investigating, said: "This is an extremely traumatic time and they are being supported by specialist family liaison officers.
"We have a team of detectives on the case who are looking at a number of lines of inquiry to establish exactly what happened. I would like to appeal to the communities of Borehamwood to help us."
He urged anyone who was in the Beech Drive area from 5pm on Boxing Day and may have information to contact Crimestoppers on 0800 555111.