According to a report in the newspaper, leaked documents say that the U.S. Anti-Doping Agency (USADA) in a letter to Montgomery allege that the American sprinter used five banned steroids plus the blood-booster EPO, human growth hormone and insulin.
USADA also suggests that Montgomery used banned performance-enhancing substances as far back as 2000, two years before he set the 100m world record of 9.78 seconds.
The newspaper said the allegations were detailed in a nine-page USADA letter sent to Montgomery on June 7.
The existence of that letter was made public by Montgomery's lawyers the following day but not its precise contents.
He had until last Friday to respond to the allegations and charges could follow this week, the LA Times added.
The agency, according to the report, also says it "anticipates testimony" regarding use of the new steroid THG in any future case against Montgomery.
If USADA finds him guilty, Montgomery would miss the Olympics unless cleared by the Court for Arbitration in Sport (CAS).
Montgomery and his lawyers have consistently denied any wrongdoing, pointing out that he has never failed a drugs test.
His attorney, Cristina Arguedas, said in a statement: "Tim Montgomery has done nothing wrong, and we believe that any fair reading of the evidence in fact supports his innocence." The statement was dated last Friday.
She said "virtually all" the allegations are linked to the files of Victor Conte, owner of the controversial BALCO laboratory in California.
Conte was indicted after a grand federal jury hearing on charges of distributing banned substances and financial irregularities. He has offered to tell all he knows about doping among top sportsmen and women in a plea-bargain.
Arguedas pointed out that Conte and Montgomery had a "bitter" falling-out which she says makes any case from him against the sprinter unreliable.
"The very nature of Conte's relationship with Tim makes these documents suspect and unreliable on their face," she said.
Montgomery was thought by U.S. commentators to have been one of at least four leading American athletes to have received a letter on June 7 from USADA regarding doping allegations.
He is the partner of triple-Olympic champion Marion Jones, who has also been investigated by USADA. No firm allegations against her have been made public.
Like Montgomery, Jones has consistently denied all doping claims against her and has never failed a drugs test.
A USADA official said Tuesday they had no comment on the report.
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