Singh and Baltimore Ravens linebacker Ray Lewis were named in a Sports Illustrated story this week as users of the spray -- derived from fast-growing deer antler velvet and containing small amounts of IGF-1, which is banned by the NFL and the PGA Tour.
Lewis, in New Orleans for the Ravens' Super Bowl battle against San Francisco Sunday, denied Wednesday he used the spray.
Singh -- described in the SI story as a "vocal supporter" of the spray -- said in a statement he has used the product but "at no time was I aware that it may contain a substance that is banned under the PGA Tour Anti-Doping Policy."
"In fact, when I first received the product, I reviewed the list of ingredients and did not see any prohibited substances," Singh said. "I am absolutely shocked that deer antler spray may contain a banned substance and am angry that I have put myself in this position."
Singh added he is "cooperating fully with their review of this matter."
The 50-year-old remains in the field for this week's Phoenix Open.