Major League Baseball has stopped testing its players for steroids for the first time in nearly 20 years due to the expiration of the sport's drug agreement, according to sources.

The halt in testing is a result of the lockout that started Dec. 2.

"It should be a major concern to all those who value fair play," Travis Tygart, chief executive officer of the U.S. Anti-Doping Agency, said.

MLB and the union declined comment on the halt.