Two San Francisco Chronicle reporters who wrote Game of Shadows, a recently-published book about the alleged steroid use of Barry Bonds, were subpoenaed Friday to testify before a federal grand jury regarding leaked court documents they obtained, the newspaper reported.

The subpoenas called for Mark Fainaru-Wada and Lance Williams to turn over copies of grand jury transcripts from the 2003 investigation into the Bay Area Laboratory Cooperative, as well as to identifywho provided them with the secret documents.

Fainaru-Wada and Williams used the transcripts in their reporting of the BALCO case that tied several prominent athletes to the use of performance-enhancing drugs.

"The San Francisco Chronicle unconditionally stands by its reporters in fighting this effort by the government to force them to reveal their confidential sources," said Chronicle executive editor Phil Bronstein, who claimed the reporters are protected under free speech laws.

"Reporters are not subject to the rules governing grand jury secrecy, which apply only to some of the people in the room during those proceedings."

Eve Burton, vice president and general counsel for Hearst Corp., which owns the newspaper, said, "The Chronicle and its reporters intend to fight the subpoenas vigorously."

Fainaru-Wada and Williams issued a statement Friday saying their articles "would not have been possible without the help of many people—people who are whistleblowers in the truest and best sense of the term."

"The government's actions raise significant First Amendment issues, and we are concerned at any attempt to stifle the public's right to know," they added.

Under U.S. federal law, it is illegal to leak transcripts of grand jury testimony but not illegal to process them.

According to excerpts of testimony reported by the Chronicle, Bonds testified he used a cream and a clear substance given to him by Greg Anderson, a personal trainer convicted in the case, but claimed Anderson told him the substances were flaxseed oil and an arthritis balm.

Bonds, who needs two home runs to tie Babe Ruth for second place on the all-time list at 714, has publicly denied knowingly taking performance-enhancing drugs on several occasions. He has never failed a drug test.

Another grand jury now is looking into whether Bonds committed perjury when he testified in the BALCO case.

Anderson and three others, including BALCO founder Victor Conte, have pleaded guilty to distribution charges.

With files from Associated Press