Behavioral specialists on Tuesday questioned a young Dutch suspect in the disappearance of Natalee Holloway (search), and a volunteer group conducted a final search of a landfill where a witness claimed to have seen men dumping a female body.

The behavior specialists from the Netherlands questioned Joran van der Sloot (search) to observe his body language and look for inconsistencies in his account of what happened the night Holloway, 18, disappeared, police spokesman Edwin Comenencia said.

Van der Sloot, 17, has changed his version of events at least once. Originally, he and two Surinamese friends told police they dropped Holloway off at her hotel and then went home May 30, the day she disappeared while on a graduation trip with 124 classmates.

Later, van der Sloot acknowledged to his mother and authorities that he was alone with the Alabama honors student on a beach near the Marriott Hotel, leaving her there but not harming her.

Massive searches near the Marriott, including the recent draining of a pond, have produced no clues. Comenencia said authorities have been searching the area for a pair of white tennis shoes van der Sloot was wearing and apparently lost the day Holloway vanished, but declined to explain their significance to the investigation.

Police escorted van der Sloot from San Nicolaas (search) prison on the eastern side of the island to the police station in downtown Oranjestad to meet with the specialists, Comenencia said. He was accompanied by his lawyers.

Van der Sloot has been repeatedly interrogated since being arrested June 9, but last month a judge ruled authorities could not question him without legal representation.

Also Tuesday, volunteers from Texas used a tractor hoe to dig through a landfill where a witness claimed to have seen men dumping and covering a blond female body two days after Holloway disappeared.

The group planned to take trained dogs through the site to try to detect human remains, said Joe Huston, search leader for Texas EquuSearch (search), the group conducting searches around the island.

Searches of the landfill over the weekend produced nothing of interest, and Huston said the volunteers would leave Wednesday unless they find something significant.

"This phase of the operation is over, though we could come again if we get additional information," Huston said.

Police searched the landfill after receiving the tip in days following Holloway's disappearance, but found nothing. He said the witness recently approached Holloway's family, who asked for another search.

Holloway's family has offered a $1 million reward for information leading to her safe return, and a separate $100,000 award for information that helps solve the mystery.