Earlier Friday, Mos' office announced prosecutors were reopening their probe into Holloway's vanishing after seeing tapes recorded by Dutch journalist Peter R. de Vries, The Associated Press reported.
Mos' office said Thursday it had "intensified" its investigation of the Holloway case because of the information from de Vries.
For his part, de Vries was promoting what he called "the most revealing report I've ever made," according to a translation of the video, posted on the Web site YouTube.
De Vries said that in an undercover camera operation, "we've found what became of Natalee and who's responsible." The report is scheduled to be broadcast Sunday on Dutch television.
But van der Sloot -- in a telephone interview from Holland -- told the Dutch television show "Pauw and Witteman" on Friday that he lied when he said he was involved in Holloway's disappearance, said one of his attorneys, Joe Tacopina.
"Joran maintains his innocence," Tacopina told CNN.