April Jones abduction: Search continues around Machynlleth
Police continuing the search for April Jones have asked the public to stand down and leave the search to trained officers.
Officers said they hoped to gain intelligence from interviews with a local 46-year-old man arrested on Tuesday.
April, 5, was with friends near her Machynlleth home when she got into a van at 19:00 BST on Monday.
The man police are questioning has been named locally as Mark Bridger.
He was found walking along a road to the north of Machynlleth by a police patrol.
Dyfed-Powys Police told a news conference on Wednesday they have been "overwhelmed" by the response from volunteers but now urged the public to leave the search to trained teams.
Supt John said more than 40 skilled officers, including dog handlers, searched overnight.
North Wales Police officers assisted Dyfed-Powys Police in the search and the South Wales force sent a team of eight search specialists.
Coastguard teams from Aberystwyth, Borth, Aberdyfi and Harlech as well as RNLI inshore lifeboat teams have assisted.
A spokesman for Milford Haven Coastguard said they expect to continue their searches along the River Dyfi on Wednesday.
Supt John thanked members of the public for their help, but said conditions were "very challenging" and he did not want officers distracted by concerns for the safety of those who wanted to help out.
"I need people to know it is a rural environment, very challenging conditions out there," he added.
"The weather yesterday wasn't great and I don't think the forecast is very good for today.
"The River Dyfi is in flood and we really do need to manage the risk of everybody there, not only the police officers, the mountain rescue team, but we are extremely concerned about large numbers of members of the public going into very challenging conditions.
"So what I am asking really is - notwithstanding the great support and the commitment that people want to show in helping us to find April - can we please leave this now to the trained and skilled people that we have?
"I don't want those officers to be distracted by the well-intentioned and enthusiastic support."
Mr John said experience suggested any breakthrough in the search for April would be at a local level, and the search is still centred on areas around the market town.
"It is likely that we are going to find somebody in the search parameter where she was last seen," he added.
Hundreds of volunteers from across the country joined the search, and some people arrived at Machynlleth leisure centre before 07:00 BST on Wednesday, but were turned away.
On Tuesday, April's family said they were "shattered" by her disappearance.
A statement, describing April as a "beautiful little girl, said: "Please, please if you have our little girl, let her come home to us."
The 46-year-old arrested man is in custody at Aberystwyth Police Station.
He was arrested at about 16:00 BST on the A487 main road north out of Machynlleth, which remains closed in both directions as far as Cross Foxes, near Dolgellau, 12 miles away.
Officers said they had been looking for him.
Det Supt Reg Bevan described him as a "significant individual", and said a vehicle police had recovered - a Land Rover Discovery - belonged to him, and was "similar to the description given by the children".
He said: "Certainly, we were looking for a vehicle matching that description. The vehicle is of extreme interest to us, as is the gentleman in custody."
April's godmother Mair Raftree, 41, from Aberystwyth, described April as "a quiet girl".
"She would never go with anybody and ask for a lift. We just want her back safely," she added.
Describing April, sweet shop owner Alyson Jones said: "She's a typical little five-year-old.
"She's bright-eyed and polite and loves coming into the shop with her family to choose her sweets.
A further news conference is expected later on Wednesday morning.
On Wednesday, Labour leader Ed Miliband said: "My heart goes out to the family of April Jones and obviously I hope there can be a successful outcome to the search for her."
Dyfed-Powys Police have asked anyone with information to contact a dedicated hotline on 0300 2000 333.