Officers investigating the disappearance of April Jones have until later this afternoon to question abduction suspect Mark Bridger.
They have until 5pm to charge or release Mr Bridger - unless they apply for a further warrant of detention.
With no sign of April since Monday evening, search teams worked through the night in the hunt for the five-year-old in Mid Wales. Their efforts were spurred on by pink ribbons of hope, donned by hundreds of well-wishers in the close-knit community of Machynlleth.
Police are holding Mr Bridger at Aberystwyth police station. They are trying to piece together his movements from 5pm on Monday until his arrest at 3.30pm on Tuesday.
April was seen willingly getting into what is believed to be a Land Rover Discovery on the Bryn-y-Gog estate where she lives at 7pm on Monday.
Mr Bridger, 46, from Machynlleth, drives a Land Rover Discovery which was seized from a local repair garage on Tuesday and fast-tracked for forensic examination. Expert search efforts have focused on a small farmhouse in the nearby village of Ceinws where he was known to be most recently living.
More than 2,500 calls with information have been received by police in response to their appeal on Wednesday.
One of the world's leading forensic psychologists who advised British and Portuguese police in the search for Madeleine McCann is reportedly helping detectives in the April case. Joe Sullivan is said to have been drafted into the Dyfed Powys police investigation team to give advice on interviewing Mr Bridger, The Times claimed.
Residents across the small Mid Wales town of Machynlleth wore the pink ribbons in a symbolic gesture of continued hope. The show of solidarity came in response to a plea from April's mother, Coral Jones, to wear her daughter's favourite colour.
Prime Minister David Cameron added his voice to the chorus of appeals for anyone with the smallest piece of information to come forward. He described the ongoing ordeal as "every family's nightmare" and urged people to "talk to the police".