Mark Bridger,a 46-year-old from the Machynlleth area, was on foot when he was detained, but his empty car was quickly recovered, police said.
Forensic officers were examining the car and described it as "a vehicle he had use of which is of interest to the inquiry." Police are also looking at whether April's abduction is linked to another attempted abduction in the Aberystwyth area around one week ago.
It comes as police confirmed that they were also looking closely at the movements of known registered sex offenders living in the area.
It is also understood that the man being questioned is known to April's family but is not a relation.
Officers said the man was arrested by a police patrol to the north of the mid Wales market town yesterday.
The arrest came in the hour before April's parents Coral and Paul Jones made a public appeal for help at a police press conference.
In a statement, read out by Detective Superintendent Reg Bevan of Dyfed Powys Police, April's family 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."
April was last seen by another child getting into the driver's side of a grey van in Machynlleth at about 7pm on Monday. Police said it appeared that she had got into the van willingly, but they did not know if she was led to the vehicle or went there herself.
Mr Bevan aded that detectives were "following various lines of inquiry".
Neighbours on the quiet former council estate of Bryn-y-Gog, from where April was taken, were in shock.
They described parents Coral, 40, and Paul, 43, as "stunned and devastated".
Mathew Harris, 22, said: "I was born and grew up on this estate and remember what it was like as a kid. Everyone played with everyone else.
"It's the same today. Kids play out together and everyone looks after everyone else. Somebody said that this estate once won an award as the safest in Powys."
Police restricted access down the A487 road heading north from Machynlleth, with searches taking place along the road. Trained officers were also seen scouring banks along the River Dyfi.