The logo of the Yomiuri Giants. The team recently won its 37th Central League championship.

TOKYO -- Samples of the same type of dietary supplement that multiple players with the Yomiuri Giants professional baseball club consumed contained banned substances, Nippon Professional Baseball Organization (NPB) announced on Sept. 25.

Since the product is not supposed to contain the materials, those linked to the manufacturer pointed to the possibility that the substances were accidentally mixed with the supplement in the manufacturing process.

According to the NPB, the dietary supplement in question is Iron SP produced by Dome Corp. After the company sent samples of Iron SP to an inspection agency in Britain in order to gain an international anti-doping certification for the product, the agency responded on the evening of Sept. 20 that the samples contained three kinds of muscle-boosting substances banned by the World Anti-Doping Agency.

According to Dome, the product is produced at a factory owned by a subcontractor in Japan. Company officials pointed to the possibility that banned substances contained in products made on the same production line for other companies were accidentally mixed with Iron SP.

Since its release, approximately 2,000 packets of Iron SP have been marketed and some 1,000 of them have been purchased. The company is now recalling the product.

Dome notified the Yomiuri Giants, to which it supplies products under an official supplier contract, about the development. The baseball club in turn interviewed players and some of them responded that they remember consuming the product in the past. The Giants then reported the matter to the NPB.

Since the samples contained only small amounts of the banned substances, the possibility is extremely slim that those who consumed Iron SP will test positive for them, according to company officials.

Although the company has supplied the product to other sports organizations, officials said they have not received any reports that those who consumed the product have tested positive for banned substances.

The Yomiuri Giants clinched the Central League pennant on Sept. 21 for the first time in five years.

(Japanese original by Yu Kishimoto, Sports News Department)