Tuesday's hearing also included testimony from Jamie Masada, the comedy club owner who first arranged for Jackson and the boy to meet, according to the source, who spoke on condition of anonymity.
Masada declined comment. He has said previously that he promised to introduce the boy to Jackson when the boy was undergoing chemotherapy in 2001.
A court order bars the media from contacting any minor called to testify before the grand jury.
It was unclear whether the hearings would continue Wednesday.
The site of the meeting Tuesday was supposed to be secret, but several news crews arrived at the scene in the morning and were prevented from entering the area by a barricade and Sheriff's deputies.
Also on Tuesday, Theodore Boutrous Jr., an attorney for news organizations, including The Associated Press, petitioned the 2nd District Court of Appeal to halt the barricade and require the location of the grand jury be disclosed.
Grand jury activities are usually confidential, and court officials have kept quiet as to whether a grand jury is hearing testimony in the Jackson case.
Jackson was charged by the district attorney late last year with seven counts of committing lewd or lascivious acts upon a child under age 14 and two counts of administering an intoxicating agent to the child. Jackson has pleaded innocent. A pretrial hearing is scheduled for Friday.
If prosecutors obtain a grand jury indictment they would not have to present evidence at a preliminary hearing to determine if the case should go to trial.
Investigators have seized about 100 pages of phone records, videos of the pop star, and a DVD of a party at his Neverland Ranch, according to court documents released in early March.
The documents also show that during a Jan. 30 search of an unidentified property, investigators seized computers, photos, videos, three videos of Jackson on compact discs and a DVD of a party at Jackson's Neverland Ranch.
A Jan. 31 search yielded computers, documents - some involving Jackson - and videotapes. The address of the property was removed, but law enforcement officials confirmed on Jan. 31 that they were searching the Calabasas residence of one of Jackson's former producers, Marc Schaffel.
Jackson has a Web site to keep fans abreast of his legal woes, as well as to celebrate his music career.
Jackson took a break from his legal troubles in California to confer with several leading black lawmakers about his upcoming mission to help fight AIDS in Africa.
Flashing a victory sign, the conservatively dressed Jackson didn't answer questions from reporters after meeting Tuesday with several members of Congress, but released a statement directed at the black lawmakers.
"What I want you to know is that whatever I can do to assist you in your fight I will do," Jackson's statement said.
Jackson, in town to accept an award for his work helping fight AIDS overseas, met privately with several black members of Congress in the office of Rep. Chaka Fattah, a Pennsylvania Democrat, to talk about his AIDS work. He is planning a trip to Africa later this year, said Rep. John Lewis, a Georgia Democrat.
Fattah called him "one of the leading celebrities in the world who has actually used his celebrity status to help people."
Jackson wanted to meet with the full 38-member Congressional Black Caucus at its Wednesday meeting, but leaders turned him down, saying they were too busy dealing with legislative issues affecting black Americans.
But several caucus members, speaking on condition of anonymity, said there was no upside politically for them to link their name to Jackson by holding a high-profile meeting with him. They also noted that Jackson has never donated any money to their causes and has never asked to speak to them before now.