The Fijian will still play in this week's Waste Management Open in Phoenix, but Tour vice-president Ty Votaw has said they will investigate the claims made in an article which appeared in Sports Illustrated.
"As we have just been made aware of the report we have not had a chance to review it in depth, but we will be looking into it," Votaw told USA Today Sports.
The article quotes former world No 1 Singh as saying he used the spray "every couple of hours...every day" and was "looking forward to some change in my body".
The deer antler spray contains IGF-1, which SI describes as a "natural, anabolic hormone that stimulates muscle growth."
Two years ago, 1999 Open champion Mark Calcavecchia was advised to stop using such a spray, and PGA Tour spokeswoman Laura Hill said at the time: "The PGA Tour regularly warns players of the risks associated with all supplements."