Mark Bridger has been arrested on suspicion of murder of missing five-year-old April Jones, police have said.
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".
"The arrest does not detract from our efforts to find her," Det Supt Reg Bevan told a press conference on Friday morning.
"Her family has been informed of this development and they continue to be supported by our specialist trained officers."
Police repeated their appeal for information on Bridger's movements on the night April went missing from the Bryn-y-Gog estate. She was seen willingly getting into what is believed to be a Land Rover Discovery at 7pm on Monday.
"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," Det Supt Bevan said.
"We also need information regarding the movements of the blue Land Rover Discovery registration L503 MEP between these times."
The 46-year-old remains in custody and will continue to be questioned. Mark Bridger was initially arrested on Tuesday on suspicion of abduction.
The brief press conference in Aberystwyth this morning was in stark contrast to the upbeat approach of many residents on Thursday.
A fund for the missing five-year-old was set up on Thursday after hundreds of people wanted to donate money to help the search.
On Wednesday it was revealed that April suffered from a mild version of cerebral palsy and would be in pain without her medication.
April's family are to decide what the money in the fund would be spent on, said Machynlleth mayor Gareth Jones.
Police said they have been "humbled" by the strength of public support, with forces around the country receiving over 2500 calls in responses to appeal to information.
Pictures of police searching the three-bedroom cottage of suspect Mark Bridger emerged on Thursday. Specialist teams have also been combing the area along the River Dyfi.
Bridger has young daughters who are known to have played with April in the area where she was snatched, near her home on the Bryn-y-Gog estate where she lives with her mother Coral, 40.
The two girls, believed to be aged seven and 10, live less than 200 yards from April's home.
Both girls have a step-sister who is the same age as April and who also regularly plays with her.
More to follow