Police investigating the murder of heavily pregnant teenager Nikitta Grender are trying to trace her mobile phone.
Detectives have also now spoken to three of the four people spotted on CCTV near Ms Grender's flat in Newport early last Saturday.
They still want to speak to the fourth person.
Ms Grender, 19, was found dead after a fire. Police are continuing to question Carl Whant, 26, on suspicion of murder.
Mr Whant, of Newport, was arrested on Wednesday. Police have until 0600 GMT on Saturday morning to question him, but could seek a further 24 hours from a magistrate.
Officers are appealing for help in finding Ms Grender's Samsung Tocco SF80 mobile phone.
Det Supt Geoff Ronayne, who is leading the investigation, said: "Although intensive searches have been carried out over the last few days, we have yet to find Nikitta's mobile phone.
"We had a very good response from the appeals we made yesterday and three out of four people captured have already come forward.
"We are grateful to the local community for their response to the media appeals."
Ms Grender's body was discovered with two stab wounds in the bedroom of her flat in Broadmead Park following a fire.
She was due to give birth to a girl, since named by her family Kelsey-May, two weeks later.
Police are continuing to search for a weapon, believed to be a knife.
The force said it had received 36 calls from members of the public following its CCTV appeal on Thursday.
A spokesman said the one remaining witness, captured on CCTV walking on Fosse Road, Pontfaen, at 0559 GMT, may have seen something relevant to the investigation and could hold vital information.
Searches are continuing in and around the estate and at two other premises in the city.
Supt Dave Johnson urged the neighbouring communities to continue helping and co-operating with the investigation.
"Our neighbourhood officers are working closely within the community to not only support the investigative team in any way they can but also to provide reassurance to the community," he said.
"The community is in shock about what has happened and we want them to know that we are grateful for their help, co-operation and patience.
"The investigative team require any information the community can give that may help in any way. The community should also know that we have local officers on the ground to help in any way they can."
Anyone with information can contact Gwent Police' major incident room on 01443 865562 or alternatively call 01633 838111 or call Crimestoppers on 0800 555111.