April was last seen getting into a light coloured van by other children playing with her near her home in Machynlleth.
Five days of searches have failed to find April, who it was revealed suffers from cerebral palsy.
Police have been searching a farmhouse in Ceinws where Bridger had recently lived.
Det Supt Reg Bevan said: “Mark Bridger has been arrested on suspicion of the murder of April Jones.
“He remains in custody in Aberystwyth and continues to be questioned.
“The arrest does not detract from our efforts to find her.
“Her family has been informed of this development and they continue to be supported by our specialist trained officers.”
Bevan called again for information relating to Bridger’s movements on Tuesday.
Suspt Ian John thanked the thousands of volunteers who’d helped in the search for April, but that they would only be using specialist teams from now on.
Reports say that two local women saw a man carrying a bin liner to the river the day after April disappeared.
Image via Dyfed-Powys Police