Investigators searched two homes in the Netherlands this morning where Van der Sloot lives or has lived, Aruba's chief public prosecutor, Hans Mos, said.
But Mos has been blocked from issuing a new arrest warrant for Van der Sloot, and went to court to appeal the ruling.
Mos said today he considers undercover tapes made by Dutch investigative reporter Peter De Vries to be "very valuable information'' that he believes will ultimately prove to be admissible in court.
"We consider it serious information and very valuable information,'' Mos told reporters at a press conference here today. "That's why we asked a judge to reopen the investigation."
A judge granted that request last week, but denied prosecutors' request for a third arrest warrant. Van der Sloot and two other Aruban men were arrested in the summer of 2005, and rearrested again last fall before they were released for lack of evidence in December.
An Aruban judge "put the threshold very, very high [for an arrest warrant for Van der Sloot] because, he said, 'this is the third time you have asked me for a rearrest,''' Mos said. "This was a tough decision for the judge, and it was also a tough decision for my office to consider a rearrest for the third time."
Van der Sloot last week insisted he had lied earlier this month when he told Patrick Van der Eem, whom he considered a close friend and confidant, that he'd panicked when Holloway appeared to go into convulsions during a sexual encounter, and he called a friend, who took her seemingly lifeless body out to sea.
Mos said he was unimpressed by those denials.
"That's exactly what we expected him to do,'' Mos said at a press conference Monday. "This was expected by us. Yet [Van der Sloot] made these statements not one time, but several times. He repeated this story."
A key question that remains unanswered is whether the undercover tapes, 20 hours in all, will be admissible as evidence. Noting that De Vries' investigation was "private," Mos seemed to indicate that fact would play in prosecutors' favor.
"We did not influence, in any way, his gathering of this information,'' Mos said.
Independent attorneys on Aruba have questioned the validity of the tapes in a court of law.
"The evidence has to be legally acceptable to a judge,'' said Lejuez. "If a policeman would be involved in an investigation like [De Vries'] without the proper instruction from a judge, it would not be legally acceptable."
Still, Lejuez said, De Vries is "a very well known Dutch reporter, who has solved many other complex cases. He has become famous for this. He has solved cases nobody else thought could be solved, using, of course, his own methods."
This is the second set of prosecutors who have sought to solve the disappearance of Holloway, who was visiting Aruba on a high school graduation class trip. She met Van der Sloot and two other local men at a raucous nightclub called Carlos N' Charlies. From there, she and Van der Sloot went to a beach in the early morning hours for an amorous encounter.
Van der Sloot, who had steadfastly insisted for more than two years, that he left the young woman on the beach, has long been the key suspect in the case.