The spray is said to include an insulin-like growth factor that was on the tour's list of banned substances.

The tour dropped its investigation last month after the World Anti-Doping Agency said deer antler spray was no longer considered prohibited because it contained just minimal amounts of the growth factor. Singh’s suit claims the tour should not have relied on WADA's list of banned substances and should have conducted independent research into whether deer antler spray even provides any performance-enhancing benefits.

Read the full article from the Associated Press here.

English: The Fijian professional golfer Vijay Singh (Photo credit: Wikipedia)