updated 5:20 p.m. ET Jan. 14, 2010

An FBI informant who was involved in Operation Equine -- the investigation that uncovered Mark McGwire's steroids use -- told the New York Daily News that McGwire used the drugs to bulk up.

This account contradicts McGwire's recent claims that he used the steroids to help him recover from injuries. The informant added that McGwire and Jose Canseco were in an "arms race," trying to outdo each other's physiques with weightlifting and steroids use. According to the informant, the steroids doses were more potent and more frequent than McGwire admitted.

"Everybody was taking steroids," the FBI informant told the Daily News. "You could not go to gyms and not see monsters. Drugs were available. They were cheap."

The Daily News reported McGwire's regimen consisted of: one-half cc of testosterone cypionate every three days; one cc of testosterone enanthate per week; the veterinary steroids Equipoise and Winstrol V, one quarter cc every three days, injected into the buttocks, one in one cheek, one in the other.

Testosterone cypionate produced quick results, lasted a long time and was used to gain strength.

The Daily News also spoke with doctor and trainers in the "steroid-soaked bodybuilding culture," and they scoffed at the idea that McGwire was using anabolic steroids for healing purposes.

Dan Gwartney, a physician in Columbia, Mo., told the Daily News that the testosterone injections McGwire received were two to four times as strong as those a patient would receive at a clinic. "It would aid in recovery but goes above that range," Gwartney said. "There would be performance enhancement for sports that depend on power, mass, an aggressive mind-set and endurance. Whether or not that was his intent, I don't know. But that dosage would enhance performance."

Trainer Anthony Roberts told the Daily News that Winstrol actually increases joint pain, rather than alleviating it. "Winstrol would literally be your last choice steroid-wise, if you were trying to rehab or prehab an injury," Roberts says.