The man being questioned by police searching for missing five-year-old April Jones has been arrested on suspicion of her murder.
The grim news was revealed as police urged volunteers who had rushed to join the hunt around the west Wales town of Machynlleth to leave it to the professionals as the "dynamics of the search have now changed".
April, who has cerebral palsy, has not been seen since Monday evening. Mark Bridger, 46, was initially arrested on Tuesday on suspicion of abduction.
Announcing the development, Detective Superintendent Reg Bevan told a press conference in Aberystwyth: "Mark Bridger has been arrested on suspicion of the murder of April Jones. He remains in custody at Aberystwyth police station, where he continues to be questioned.
"The arrest does not detract from our efforts to find April and we remain committed to finding her. Her family has been informed of this development and, as you would expect, they continue to be supported by a family liaison officer."
Mr Bevan spoke only briefly to reveal the development. Looking tired and drawn on the fifth day of searching, he renewed the appeal for information regarding Bridger's movements.
He said: "We are looking to trace the movements of Mark Bridger between 6.30pm on Monday and 3.30pm on Tuesday and any sightings of him between these times. We also need information regarding the movements of the blue Land Rover Discovery, registration L503 MEP, between these times."
Superintendent Ian John acknowledged again that volunteer searchers had played a "vital part" in the hunt for April so far. But things have changed with the announcement that Mr Bridger is now being held on suspicion of murder, he said.
April was seen willingly getting into what is believed to be a Land Rover Discovery on the Bryn-y-Gog estate at 7pm on Monday. Bridger, from Machynlleth, drives a Land Rover Discovery which was seized from a local repair garage on Tuesday and fast-tracked for forensic examination. Detectives have until this afternoon to question him unless they apply for a further warrant of detention.
At the press conference, Mr John said that because of today's "significant development", it was no longer appropriate for the many volunteers who had joined the hunt for April to continue searching: "We want to acknowledge, and are extremely grateful for, the efforts of the community volunteers who have supported the professional searchers in trying to locate her. They have been a vital part of our team throughout this search operation. Quite frankly, their commitment has been an inspiration to us all."