A man remains in custody on suspicion of murder, a week after pregnant teenager Nikitta Grender was found stabbed to death in her burning flat.
The body of the 19-year-old was discovered in her bedroom in Broadmead Park, Liswerry, Newport, by firefighters early last Saturday.
She had been stabbed twice and her room set alight to disguise the killing, police have said.
Gwent Police arrested 26-year-old Carl Whant on Wednesday.
Police had until 0600 GMT on Saturday morning to question Mr Whant have been granted another 24 hours.
Meanwhile, detectives say they have now spoken to three of the four people identified on CCTV in the area near Ms Grender's flat around the time of her death, but still want to speak to the fourth person.
They are also still trying to find Ms Grender's mobile phone, a Samsung Tocco SF80.
Ms Grender was two weeks away from giving birth to a girl, named Kelsey-May by her family.
Police are continuing to search for a weapon, believed to be a knife.
A number of items, including two knives, are being forensically examined after a search of streams and culverts in the locality by a specialist search team from neighbouring South Wales Police.
Anyone with information can contact Gwent Police' major incident room on 01443 865562 or alternatively call 01633 838111 or call Crimestoppers on 0800 555111.