For the magistrates to have authorised the extension of his detention, the Bench has to be satisfied that there is the makings if a case against him (and the nature and strength if that has obviously not been released) and that there is a realistic prospect of securing more relevant evidence in the extra time. That might be further forensic results as well as information from sightings (they had over 2500 calls from the public to process).
If he is to be charged, we'll probably know by mid-afternoon (or if released, he'll be quietly out before the deadline so he move to somewhere where he will not be in immediate danger).
Appeals for sightings may assist the search. It's also important to any future case, for if he is claiming he was doing something unconnected to April's disappearance, he will not have to opportunity later to state that his version of events was not adequately investigated.