A court ruled Friday that DNA samples collected from the Dutch youth jailed in the disappearance of an Alabama teenager and one of his friends could not be used in a case against them.

No one has been charged in the disappearance of 18-year-old Natalee Holloway (search), who disappeared on the final night of a high school graduation trip to the Dutch Caribbean island. No trace of her has been found.

Joran van der Sloot (search), 17, the only person who remains jailed in the case, has admitted he spent part of the evening with her. He has said through his family and lawyers that he had nothing to do with her disappearance.

The court ruled Friday that prosecutors did not clarify what his DNA samples would be compared with, but said the prosecution could request new DNA samples from van der Sloot if they had documents clarifying what would be used in the comparison.

In the case of Satish Kalpoe (search), van der Sloot's friend who was jailed and then released in the case, the court ruled there was not enough evidence to warrant using the tests.

Also Friday, police and a volunteer group from Texas searched a landfill in hopes of finding clues about what happened to Holloway. Edwin Comenencia, the police spokesman, declined to say what prompted the search.

"So far they have found nothing," he said.

Van der Sloot is the only person detained as a suspect in the case. Satish, 18, and his 21-year-old brother Deepak Kalpoe (search), were previously held and released.

Holloway, from Mountain Brook, Ala., vanished after an evening at a nightclub that she left with the three young men, hours before she was to fly home at the end of the trip with 124 classmates.