NEW YORK (Reuters) - Colorado Rockies minor leaguer Mike Jacobs became the first North American professional sports league athlete to be suspended for testing positive for human growth hormone, Major League Baseball (MLB) said Thursday.

The 30-year-old first baseman, who has played six seasons in the major leagues, received a 50-game suspension after testing positive for HGH -- the first such case since MLB instituted blood tests for doping in the minor leagues.

Jacobs, who had played for the New York Mets, Florida Marlins and Kansas City Royals, was leading the Rockies' Triple-A club in Colorado Springs in home runs (23), doubles (30) and runs batted in (97).

The Rockies announced they were releasing Jacobs.

"There is no place in baseball for such substances, and we have and will continue to do what we can to eliminate them from our game," the National League club said in a statement.

The World Anti-Doping Agency (WADA) said the finding, which also marks the first time an athlete tested positive for HGH in the United States, is significant and sends a strong message.

"It is yet further indication of the fact that the test works and that it should be used more widely," WADA chief David Howman said in a statement.

"It is clear that HGH is one of the biggest threats to sport right now and has been for many years. Athletes have taken it with impunity because it was not detectable."

Jacobs, who compiled a .253 batting average with 100 home runs and 310 runs batted in during 556 major league games, said he took HGH to try and recover from injuries and hopes to resume his career following his ban.

"A few weeks ago, in an attempt to overcome knee and back problems, I made the terrible decision to take HGH," Jacobs said in a statement.

"Taking it was one of the worst decisions I could have ever made, one for which I take full responsibility. I apologize to my family, friends, the Colorado Rockies organization, Major League Baseball and to the fans."

(Reporting by Larry Fine, Editing by Frank Pingue)