Specialist search teams have endured torrential rain as they worked through the night in the hunt for missing April Jones.
With the investigation entering a fifth day, detectives have until 5pm to charge or release their main suspect Mark Bridger - unless they apply for a further warrant of detention.
The search for April continued overnight in persistent rain. At around midnight, a specialist unit from the London-based British Transport Police set out from Machynlleth Leisure Centre to join in the operation.
Welsh Mountain Rescue teams continued their efforts searching through rugged terrain near the town.
Lance Paget, search manager for Longtown Mountain Search and Rescue Association, said, "The police have given us an area to search that may be of interest to them and we're just doing what we can."
As his team picked their way through bushes along a roadside, he added: "We're all volunteers, so some people are doing their jobs during the day then coming here at night or they've taken time off work."
An ambulance crew is also on 24-hour standby in case April is found.
Shane North from the Welsh Ambulance service said: "The thing we're hoping for is that April will be found alive and well, but if she has been exposed to these conditions she may be very sick so we want to be on hand to give her immediate medical attention when they find her."
Police say they have received 2,500 calls following an appeal for information from the public.
Speaking at a news conference, Superintendent Ian John said officers from all 44 forces across the UK are filtering through the information for clues to the little girl's disappearance.
It has also been revealed that April's father Paul has a degenerative eye disease and is unable to take part in the searches.
Machynlleth Town Council has set up an appeal fund for April and her family.
Councillor Mike Williams told Sky News: "We've set up the fund as a result of all the requests we've had - not just from the town but all across the UK."
Police are searching the three-bedroom cottage, out buildings, and garden of Mr Bridger, in the hamlet of Ceinws.
They are also launching a major search of the nearby Dyfi River, involving dog handlers.
Officers have searched a guest house where Mr Bridger is understood to have worked recently.
April's family have launched a pink ribbon campaign to support the hunt and revealed that the little girl was suffering from cerebral palsy.
Her favourite colour is now tied in ribbons on nearly every gate and doorway in Machynlleth.
Residents across the small mid Wales town donned pink ribbons in a symbolic gesture of continued hope.
April has been missing since around 7pm on Monday when she vanished while playing with friends near her home on the Bryn-y-Gog estate.
Police are appealing for anyone who saw Mr Bridger or his blue Land Rover Discovery, registration number L503 MEP, in the hours between April's disappearance and his arrest at 3.30pm on Tuesday.
Estate agents J H Jones in Machynlleth say his farmhouse, called Mount Pleasant, was sold by them last year. It was on the market for £170,000.
Prime Minister David Cameron joined police in urging anyone with information about the whereabouts of the "lovely girl" to speak to officers.
:: Anyone with information relating to the case is asked to call Child Rescue Alert Line on 0300 2000 333.