NEW YORK — Baseball investigator George Mitchell has received an extensive paper trail documenting performance-enhancing drugs sent to players by former New York Mets clubhouse attendant Kirk Radomski, a person familiar with the probe said Monday.

Among the documents Mitchell has obtained are invoices detailing the substances sent to players, the person said, speaking on condition of anonymity because Mitchell hasn't authorized details to be made public.

Mitchell likely will issue his report on steroids in baseball by the end of the year, lawyer Thomas Carlucci said during a conference call with club officials Friday. Carlucci told them they should assume the report will name names.

Radomski pleaded guilty in April to distributing steroids to major league players from 1995-2005 and laundering money, and he was required as part of a plea agreement to cooperate with Mitchell, a former Senate majority leader who is a director of the Boston Red Sox.

An affidavit signed by IRS special agent Jeff Novitzky in December 2005 contains the names of players Radomski dealt with, but the names were blacked out when a copy of the affidavit was unsealed in April. Scott Schools, the U.S. attorney in San Francisco, said then that Radomski admitted providing steroids, human growth hormone, amphetamines and other substances to "dozens of current and former Major League Baseball players and associates."

A federal judge rejected a request by Hearst Corp. to unseal the affidavit, and the company has asked the 2nd U.S. Circuit Court of Appeals to review the case.

Mitchell declined comment on Radomski, who is to be sentenced Nov. 9. Radomski met with Mitchell this year and revealed the names of players who bought steroids from him, reported in August.

Radomski's lawyer did not return a telephone call seeking comment.

Republican presidential candidate Sen. John McCain said Monday it was possible Congress will hold another hearing on steroids in baseball.

"Congress quite often goes in for a little headline grabbing, and then we move on because our attention span is rather short," McCain said on "The Dan Patrick Show." "I don't think that hearings are especially necessary until Sen. Mitchell issues his report."

McCain said it was a mistake not to include Barry Bonds in the March 2005 hearing that featured Mark McGwire, Sammy Sosa and Rafael Palmeiro.

"I think that maybe in retrospect that it probably would have been a good idea to do so, but that decision was made over in the House of Representatives," he said.

McCain said he considers Hank Aaron the home run king, even though Bonds has 762 homers, seven more than Aaron's total.

"Maybe an asterisk should be after Mr. Bonds' name," McCain said. "I'm not trying to impose it. I'm not telling Bud Selig to do it. I'm just saying that happens to be my personal opinion."