Ian Huntley admitted spotting Holly Wells and Jessica Chapman just hours after telling other searchers he had not, his Old Bailey trial has heard.
The girls disappeared last year
Retained firefighter David Hobbs said Mr Huntley told him he saw the girls on the day they vanished in Soham.
In an earlier meeting with searchers and a later encounter with Holly's father, Mr Huntley denied seeing them.
The court was also told Mr Huntley denied having keys to the building where the girls' clothes were found.
Mr Huntley denies murdering the girls, while his former girlfriend Maxine Carr denies helping an offender and conspiracy to pervert the course of justice.
Best friends Holly and Jessica went missing after a family barbecue at the Wells' home in the Cambridgeshire town on 4 August 2002.
Their bodies were found 13 days later in a ditch near RAF Lakenheath.
The Old Bailey heard on Friday that Mr Huntley had been seen on several occasions by searchers and police on the night the girls vanished, and appeared "calm".
The court had heard on Thursday that at 2230 BST Mr Huntley was asked by a group of
people if he had seen the girls and said he had not.
Mr Hobbs said at around 0230 BST, after an hour of searching together, Mr Huntley mentioned the two girls had passed his house at 1830 BST the previous day.
He and a colleague told him to tell the person in charge.
When Mr Huntley's QC Stephen Coward suggested the caretaker's admission was only made after one of the searchers mentioned the missing girls were wearing red Manchester United shirts, Mr Hobbs agreed.
When Holly's father and a colleague saw Mr Huntley at Soham College at 0430 BST he said he had not seen Holly and Jessica.
Policewoman Anna Burton told the court Mr Huntley had shown her round the college with her tracker dog, and that he was "very pleasant... very helpful".
He said he "did not have keys" to one building - where police later found charred remains of the girls' clothing.
Mr Coward suggested Mr Huntley had told her he would go back to the house and get the keys to the hangar, but she said: "I asked him if he had the keys to that
building and he said, no, he didn't."
Police found the the keys in his house when they searched it 12 days later.
Schoolteacher Susan Hurrell said she was "excited" when Mr Huntley later told her he had spotted the girls.
She took him to speak to a female police sergeant, but he seemed "reluctant", she said.
In giving her evidence, Sergeant Pauline Nelson said Mr Huntley told her he had seen the girls at 1730 BST.
Huntley's car 'gone'
When asked why he hadn't mentioned it previously he said he had told fellow searchers but "didn't think it was necessary" to inform the police.
On the eighth day of the trial of Mr Huntley and his ex-girlfriend Maxine Carr, Scott Day told the court he helped his business partner Kevin Wells drive around searching for the girls from 2215 BST.
They saw Mr Huntley three times during the night.
On their last meeting at Soham College, the caretaker said he was there to write a note to say he'd be late for work the next day because he had worked through the night, Kevin Wells' business partner told the court.
Another local witness, Stuart Smith told the court he had joined the search after pub closing time.
He said he was used to seeing Mr Huntley's red Ford Fiesta parked outside his house, but that as they searched the area there were no lights on and no car present.
The prosecution alleges that Mr Huntley killed the girls on the night they went missing, put their bodies in the Fiesta and drove them to the Lakenheath site where they were eventually found.
The case was adjourned until Monday morning.