The Associated Press

Though Marion Jones was not among four athletes to receive letters about possible drug violations, the U.S. Anti-Doping Agency isn't done with her yet.

The drug scandal, which already has taken down four top athletes, threatens to bar several more - and the sport's biggest star, Jones, remains under investigation.

Jones, who met with USADA officials last month about possible doping evidence against her, received a letter from the agency Tuesday asking follow-up questions.

"USADA asked us the same questions they asked us during our May 24 meeting with them," said a representative for Jones, who spoke on condition of anonymity.

USADA spokesman Rich Wanninger said Wednesday he could not comment on the case involving Jones, who won an unprecedented five track medals - three of them gold - at the 2000 Olympics.

Jones' boyfriend, 100-meter world-record holder Tim Montgomery, was among four prospective Olympic medalists who received letters Tuesday informing them that the USADA is pursuing possible doping cases against them that could result in bans from the Athens Games.

Jones issued a statement about Montgomery Tuesday: "I support him and believe in him, and I have no doubt that if a fair process is applied, that Tim will be racing for gold in Athens this August."

Sources close to the situation, on condition of anonymity, identified the other athletes who received USADA letters as Alvin Harrison, an Olympic silver medalist in the 400 meters, and sprinters Chryste Gaines and Michelle Collins.

The letters to Montgomery and the other three are the first formal step in USADA's attempt to punish athletes based on documentary or testimonial evidence instead of a positive drug test. If found to have committed doping offenses, the athletes could face two-year bans.

Montgomery's lawyer, Cristina Arguedas, said her client has done nothing wrong and will fight any attempt to keep him from running in the U.S. Olympic trials in Sacramento, Calif., on July 9-18 or at the Aug. 13-29 Summer Games. Jones, too, has threatened to sue if the USADA tries to bar her.

Under USADA regulations, Montgomery and the other three athletes have 10 days to respond to the letter. Everything then is forwarded to a USADA review board, which recommends whether to proceed with a case.

Sprinter Kelli White, shot putter Kevin Toth and hammer thrower Melissa Price will miss the Olympics because of steroid violations. Hammer thrower John McEwen has been banned for two years.