The preliminary DNA results, which are subject to verification tests, could assist prosecutors if they seek an indictment of Clemens on charges that he lied about the use of steroids. Scientists at the Anti-Doping Research Institute in Los Angeles are trying to determine whether the syringes ever contained steroids and human growth hormone, the sources said.

Clemens told the House Oversight and Government Reform Committee last year that he has never taken performance-enhancing drugs. McNamee testified he injected Clemens nearly 40 times with steroids and human growth hormone from 1998 to 2001.

McNamee's attorneys have said their client gave federal investigators syringes, gauze pads and other items that he claimed he used to inject Clemens. He stored the items in a box in his basement.

Clemens and his defense team have long challenged McNamee's credibility, saying the former trainer has lied about the pitcher's alleged drug use. Rusty Hardin, Clemens' Houston-based defense attorney, said the DNA tests "won't matter at all."

"It will still be evidence fabricated by McNamee," Hardin told the paper. "I would be dumbfounded if any responsible person ever found this to be reliable or credible evidence in any way."

Clemens voluntarily gave a DNA sample to federal authorities conducting the genetic tests, the sources said.

Clemens has said he was injected with vitamin B-12 and a painkiller over the years. Without any evidence of steroids or human growth hormone in the syringes, prosecutors will face a tougher time convincing jurors that Clemens was injected with those substances, legal experts said.