Fearing the investigation into the disappearance of Natalee Holloway (search) has gone cold, a U.S. senator is calling for the Aruban government to allow the FBI to get more involved in the case.

Sen. Richard Shelby (search) wants the FBI to have full access to evidence in the case and he wrote a letter to FBI Director Robert Mueller to gain support for his idea. Shelby, a Republican, represents Alabama, Holloway’s home state, in the Senate.

Aruban officials said the FBI is welcome to send more people, but government spokesman Ruben Trapenburg said he did not think the extra U.S. effort would help find the young woman who has been missing for a month.

Holloway family attorney Vinda De Sousa said of Aruban officials: “They will consider every option and possibility,” when asked about bolstering the FBI's influence.

On the Dutch-Caribbean island, 20 Aruban investigators are assigned to the case, three of them are technology experts working solely on chatroom communication, text messaging and cell phone calls made between the three suspects in the days after the 18-year-old went missing.

The FBI already has helped in the effort. Massive searches by FBI agents, Dutch Marines (search), Aruban police and thousands of islanders have produced no trace of Holloway, who was celebrating her graduation from high school in Mountain Brook, Ala., when she disappeared.

Dutch teenager Joran van der Sloot, 17, and his friends, Surinamese brothers Deepak Kalpoe, 21, and Satish Kalpoe, 18, were the last people seen with Holloway the night she vanished. The three were questioned in the days after the disappearance but were not arrested until June 9.

Two other men detained in the case — van der Sloot's father, Paul, and party boat disc jockey Steven Croes — have been released.

On Thursday, Aruba Attorney General Caren Janssen (search) said investigators have found no evidence to suggest that Holloway was dead.

"There are no traces or facts to come to the conclusion that Natalee is no longer alive," Janssen told The Associated Press in a telephone interview.

Janssen declined to reveal what other evidence investigators might have. But she said she could prosecute a case in Holloway's disappearance even if her body is not found.

Holloway's stepfather, George "Jug" Twitty, said the family was not surprised by Janssen's comments and was not losing hope the truth would be found.

"We may have no physical evidence, but there is a lot of other evidence of what may have happened in this case," Twitty said.

Janssen, who has been tightlipped during the investigation, said she had decided to speak out because "there has been so much misinformation in the American press."

"I'm the lead prosecutor and I want to show that we are not a bunch of cowboys here," she said.

Janssen declined to be more specific about what she believed had been reported inaccurately.

Paul van der Sloot, an island judicial official, was arrested June 23 but released a few days later when a judge ruled there was not enough evidence to hold him.

Janssen said the elder van der Sloot gave his son and the Kalpoe brothers legal advice, telling them that "without a body there is no case."

"He confirmed to me that he told them that a few days after she disappeared," Janssen told the AP.

Janssen also alleged Paul van der Sloot, a 52-year-old judge in training in Aruba, obstructed authorities' investigation by asking one of his son's friends, who had been interrogated, what he told police.

But Janssen said Paul van der Sloot was detained for being a suspect in the disappearance, not for obstructing the investigation.

Calls to the van der Sloot residence Thursday seeking comment were not answered.

A group of volunteer rescuers from Texas, which started searches Saturday, began a partial pullout from Aruba on Wednesday, with nine of the 27 volunteers returning home. But the group said it planned to bring in replacements for those who had left.

And as more than a month has elapsed since the teen's disappearance, her family holds onto hope that she will be found.

Said family attorney De Sousa: “They’re trying to hold up and keep their spirits high.”

The Associated Press contributed to this report.