Aruban authorities have brought in experts from the Netherlands and sent a prosecutor to consult with the FBI as they seek to solve the disappearance of missing Alabama teen Natalee Holloway (search), officials said Monday.

The reward in the case rose to $1 million.

The four experts from the Netherlands traveled to the Dutch Caribbean island to assist with interrogations while two members of the team investigating the Holloway case traveled to the FBI crime lab in Quantico, Va., the public prosecutor's office of Aruba said.

Aruba has agreed to show transcripts of interrogations to the FBI, which is acting in an advisory role in the high-profile case, in a sign of increased cooperation that drew praise from the family of the Mountain Brook teen who vanished on the last night of a high school graduation trip.

"I'm really so grateful to the Aruban officials who have made it possible to release this information," the teenager's mother, Beth Holloway Twitty (search), said after announcing that the reward for information leading to her safe return had been increased to $1 million.

A family spokeswoman in Birmingham said the reward was increased after Holloway's relatives received an offer from an anonymous benefactor.

No one has been charged in the case. Joran van der Sloot (search), the 17-year-old son of a judge in training on the island, has been detained as a suspect.

Aruban authorities agreed to provide the transcripts after the country's prime minister sent a letter to Attorney General Karin Janssen urging prosecutors to give the FBI "complete access" to materials from the investigation to the extent allowed under Dutch law, which governs the territory.

The FBI has also collected a sample of hair found on duct tape along the shore of the island for a DNA analysis. The agency has advised Aruban authorities in the six-week investigation into the disappearance of Holloway but previously had not had access to documents.

The public prosecutor's office said in a statement that Amalin Flanegin, a senior member of the prosecution team, and a police investigator would be at the FBI crime lab for a week with materials gathered during the investigation to discuss the case. They did not specify the materials.

Holloway, 18, disappeared May 30, hours before she was to catch a return flight to Alabama, at the end of a trip with 124 classmates. Extensive searches of the island have failed to find a trace of her, and Twitty said she hoped the increased reward — plus a separate offer of $100,000 for information that solves the mystery — will spur action in the case. Previously, the family offered $200,000 for her safe return.