At a press conference to plead for help, Coral Jones sobbed as she said: "It's been 36 hours since April was taken from us. There must be someone out there who knows where she is.
"We are desperate for any news, please, please help find her."
It follows Coral and husband Paul's moving appeal for information about their daughter yesterday.
They said: "Last night our lives were shattered when our beautiful little girl April, who was playing with friends, was taken from us.
"We are devastated and our lives have stopped. Please please if you have our little girl let her come home to us."
This morning police issued a photograph of a Land Rover Discovery belonging to a 46-year-old man who has been arrested on suspicion of abduction and who they have named as Mark Bridger - although officers stressed that he is one of several lines of inquiry being pursued.
They have appealed for anyone who may have seen the vehicle or its owner between Monday at 5pm and 3.30pm on Tuesday to contact them.
Detective Superintendent Reg Bevan, who is leading the inquiry, said: "We can confirm that we have in fact arrested Mark Leonard Bridger and he remains in custody in Aberystwyth.
"We appeal to anyone who has seen him in the past few days. We are in the process of piecing together his movements and that of his vehicle from 5pm on Monday to 3.30pm on Tuesday afternoon when Mark Bridger was arrested.
"He was wearing a camouflage green jacket and black waterproof over trousers when he was arrested."
Dyfed-Powys Police told an earlier news conference they had been 'overwhelmed' by the response from volunteers but now urged the public to leave the search to trained teams.
Superintendent Ian John said more than 40 skilled officers, including dog handlers and helicopters with thermal imaging, searched overnight and resumed at daybreak.
Police have asked anyone with information to contact a dedicated hotline on 0300 2000 333.