SAN FRANCISCO -- Federal authorities probing an alleged steroid distribution ring have seized the results and samples of drug tests on selected major league baseball players from a drug-testing lab, a spokesman for the lab said Friday.

Internal Revenue Service agents served a search warrant to obtain "documentation and specimens" from a Quest Diagnostics lab in Las Vegas, Quest spokesman Gary Samuels said.

Samuels would not say whether IRS agents took the drug-test results or specimen of Barry Bonds, but said the agents took materials consistent with a federal subpoena that had sought test results and specimens from the San Francisco Giants' slugger and fewer than a dozen other players. Among them were New York Yankees Gary Sheffield and Jason Giambi.

The raid occurred Thursday, shortly after the Major League Baseball Players Association filed a motion in a San Francisco court seeking to squash that subpoena.

IRS spokesman Mark Lessler and U.S. Attorney's spokeswoman Ji-Yon Yi both said Friday they could not comment.

Samuels said the IRS agents served the search warrant on the Quest lab after obtaining a coded list from California-based Comprehensive Drug Testing that matched players to the results and the samples.

Teterboro, N.J.-based Quest and Comprehensive Drug Testing, of Long Beach, did the tests last year for Major League Baseball, which was trying to determine the prevalence of steroid use among players. When more than 5 percent of those tests came back positive, the major leagues began a new testing program this season.