The mother of two brothers detained in the Natalee Holloway (search) case acknowledged that her sons initially lied about the night of the 18-year-old's disappearance, but said it was because they were protecting another suspect.

Deepak and Satish Kalpoe first told police that they dropped off Holloway at the Holiday Inn where she was staying because they had agreed on that version of events with Joran van der Sloot (search), the 17-year-old also jailed in the case, said Nadira Ramirez, the Kalpoes' mother, in an exclusive interview with FOX News' Greta Van Susteren.

Click here to watch part one of the interview with Ramirez. Click here to watch part two.

But Joran's mother, Anita van der Sloot, told The Associated Press on Thursday that Joran now admits to being alone with Holloway on a beach. Still, Joran denies hurting Holloway.

Ramirez said she talked to her sons about what they first told police.

"They said he's our friend and we lied to cover him," she told FOX News.

Ramirez also described what her sons told her about May 30, the day of Holloway's disappearance: Deepak, 21, and Satish, 18, picked Joran and Holloway up somewhere on Aruba after Deepak got off work at an Internet cafe. As they drove, the two brothers sat in the front seat while Holloway and Joran kissed in the back. "[Deepak] said he was getting a little upset” that they were doing that in his car, said Ramirez.

But she said her sons told her they didn't even know Holloway, who they said had been drinking that night and wasn't walking steadily.

"They don't know nothing about her. Only they know that she was with Joran. ... She didn't even introduce herself to them."

Ramirez said she didn't doubt that her boys were now telling the truth: "They always come clean with me."

Separately Friday, a source familiar with the investigation told FOX the FBI only has three agents in Aruba now, down from seven earlier. The source, who requested anonymity, said the team has been reduced because there is not much to investigate now that arrests have been made.

Meanwhile, Joran's father was himself in custody after being arrested Thursday. After an initial interrogation, a judge ordered Paul van der Sloot (search) held at a police station jail for another 48 hours.

Aruban prosecutor's office spokeswoman Mariaine Croes said Paul van der Sloot was arrested under "reasonable suspicion" in the disappearance of Holloway.

"We have a reasonable suspicion at this point that he may be involved in the disappearance of Miss Holloway," Croes told FOX Friday morning.

"The decision to bring him in and arrest him was based on the police investigation done on him up to this point," Croes said, when asked whether he was brought in over anything his son may have said to police.

Aruba government spokesman Ruben Trapenberg told FOX the elder van der Sloot may have been arrested after investigators heard inconsistencies in media interviews, like the one with FOX News' Greta Van Susteren, and what he told police.

Trapenberg added Paul van der Sloot has been cooperative with investigators.

Paul van der Sloot is an island judicial official.

The source told FOX the FBI knew about the arrest of Paul van der Sloot in advance but did not accompany authorities to the house because of political sensitivities.

FOX was told computer hardware taken from the van der Sloot home on June 15 will be sent to The Netherlands for inspection.

Before his arrest, Paul van der Sloot told FOX News that he was sure his son had nothing to do with Holloway's disappearance.

"We still believe in Joran," said Paul van der Sloot.

Joran van der Sloot and the Kalpoes were arrested 10 days after Holloway disappeared. Police say Joran van der Sloot met Holloway at a casino two days earlier.

Beth Holloway Twitty, Natalee Holloway's mother, has insisted that the three know what happened to her daughter and that police should press them harder to tell the truth. She has asked why the three were initially released after only a couple of hours of questioning, and arrested more than a week later.

Anita van der Sloot also questioned that tactic. She told FOX News: "Joran should have been interrogated from the beginning. But they let the kids go."

Holloway disappeared May 30. The 18-year-old Mountain Brook, Ala., woman was celebrating her high school graduation with a trip to Aruba with other students.

A fourth man detained in the case, 26-year-old party boat disc jockey Steve Gregory Croes (search), said he knew one of the two Surinamese brothers arrested with Joran van der Sloot from an Internet cafe, according to his boss, Marcus Wiggins. Wiggins' boat, the Tattoo, docks near the Holiday Inn.

FOX News' Greta Van Susteren, Catherine Herridge and The Associated Press contributed to this report.