A 20-year-old man has been arrested on suspicion of murder after two shop workers were found dead in the centre of Cardiff.
The bodies of 33-year-old Lee Simmons and a 21-year-old Zoe Morgan were discovered near the Cardiff Castle end of Queen Street shortly before 6am.
Matalan has confirmed they both worked at its Queen Street store.
Although a post-mortem is yet to be carried out, both victims are believed to have suffered stab wounds.
Police say they are not looking for anyone else in connection with the incident.
The suspect, from Castleton, Newport is being held at Cardiff Bay police station.
He was arrested with the assistance of Gwent Police officers at an address in Castleton within an hour of the incident being reported.
Police believe he was known to Miss Morgan and Mr Simmons.
Chief Superintendent Belinda Davies said: "This incident occurred in the main shopping area in the heart of the city in rush hour and it has no doubt shocked the community of Cardiff.
"We are in the very early stages of the investigation but I would like to add that at this stage we believe the suspect was known to the victims and it was not a random assault.
"I would like to dispel speculation circulating as to the motive behind this tragic incident and make it clear that this is not being linked to terrorism, and any links to the homeless community are unfounded."
Earlier, South Wales Police said it was aware of graphic photographs from the scene being circulated on social media, and urged the public to use their "better judgment" when sharing and using images online.
The pedestrianised area of Queen Street where the bodies were discovered was cordoned off, forcing several stores to remain closed.
Matalan chief executive Jason Hargreaves said: "It is with great sadness that we can confirm that there was a fatal stabbing in Queen Street, Cardiff, this morning.
"Both of the victims worked at our Cardiff branch so understandably all of our colleagues are receiving our full support. We request that they are given the space to deal with this at this difficult time.
"That is all we know at this stage and we are working tirelessly with the police in their investigations.
"We extend our condolences to the families of everyone involved."
Miss Morgan stated on her Facebook page that she had a degree in fashion marketing and retail design from the University of South Wales.
A university spokeswoman said: "We are deeply saddened to learn of the loss of Zoe, who had been a popular and well-liked student who was now doing well in her chosen career."
A police spokesman said: "The families of both victims have asked that the media refrain from contacting them and that they be allowed to grieve in private."