NEW YORK —David Ortiz thinks legal supplements and vitamins likely caused him to land on a list of alleged drug users seized by the federal government, and Major League Baseball and the players' association said some of the names on the list never tested positive for steroids.

MLB said in a statement Saturday that at most 96 urine samples tested positive in the 2003 survey — and the players' association said 13 of those were in dispute.

The government seized the samples and records the following year from baseball's drug-testing companies as part of the BALCO investigation. The list of 104 players alleged to have tested positive has been the subject of a five-year legal fight with the union trying to force the government to return what federal agents took during raids.

"I definitely was a little bit careless back in those days when I was buying supplements and vitamins over the counter — legal supplements, legal vitamins over the counter — but I never buy steroids or use steroids," Ortiz said during a news conference before his Boston Red Sox played the New York Yankees. "I never thought that buying supplements and vitamins, it was going to hurt anybody's feelings."

The New York Times reported last month that Ortiz and Manny Ramirez were on the 2003 list and said earlier that Sammy Sosa was on it. In February, Sports Illustrated reported Alex Rodriguez was on it, and Rodriguez later admitted using Primobolan.

Ortiz said that when he met with union lawyer Michael Weiner in 2004, he wasn't told he tested positive for steroids. Weiner, who has been designated to succeed union head Donald Fehr, said that because the list is under court seal, the union can't confirm to Ortiz that he tested positive, only that he was on the list.

"I want to apologize to fans for the distraction, my teammates, our manager," Ortiz said, flanked by Weiner, with Boston manager Terry Francona standing behind and to the side. "This past week has been a nightmare to me."

Ortiz said he has tested negative about 15 times since baseball's program with penalties began in 2004 and additional times for the World Baseball Classic. The Red Sox issued a statement backing him.

"There are substantial uncertainties and ambiguity surrounding the list of 104 names," the Red Sox said. "David Ortiz is a team leader, and his contributions on the field and in the community have earned him respect and a special place in the hearts of Red Sox Nation."

Citing court orders, Weiner wouldn't say whether the union asked courts to authorize an investigation into the source of the leaks. He did say that if the union wins the legal fight to have the records returned, which may end up before the Supreme Court, it likely would comply with requests from players on the list to tell them what they were said to have used.

"Given the uncertainties inherent in the list, we urge the press and the public to use caution in reaching conclusions based on leaks of names, particularly from sources whose identities are not revealed," Major League Baseball said in a statement.

Weiner said a player alleged to be on the list "finds himself in an extremely unfair position; his reputation has been threatened by a violation of the court's orders, but respect for those orders now leaves him without access to the information that might permit him to restore his good name."

"Accordingly, the presence of a player's name on any such list does not necessarily mean that the player used a prohibited substance or that the player tested positive under our collectively bargained program," Weiner said.

The survey was designed to determined whether baseball needed mandatory random drug testing with penalties starting in 2004, with a 5 percent threshold for positives triggering future testing. While the exact number of 2003 positives was subject to dispute, the sides never worked that out because they agreed the percentage was over the threshold.

"Substantial scientific questions exist as to the interpretation of some of the 2003 test results," Weiner said. "The more definitive methods that are utilized by the lab that administers the current drug agreement were not utilized by the lab responsible for the anonymous testing program in 2003. The collective bargaining parties did not pursue definitive answers regarding these inconclusive results, since those answers were unnecessary to the administration of the 2003 program."

Under the rules of the 2003 testing, Weiner said "legally available nutritional supplements could trigger an initial 'positive' test under our program."

"Each 'test' conducted in 2003 actually consisted of a pair of collections: The first was unannounced and random, the second was approximately seven days later, with the player advised to cease taking supplements during the interim," Weiner said. "Under the 2003 program, a test could be initially reported as 'positive,' but not treated as such by the bargaining parties on account of the second test."