Ostapchuk tested positive for metenolone, an anabolic agent. The announcement came just hours after the curtain came down on the 30th Olympiad in London.
"I was tested twice more in London but I don't have any idea how this thing ended up in my body. I'm going to fight this allegation because it can't be possible," Ostapchuk reportedly told local media in Minsk.
"In total, I've been tested 16 times since April. You must be a complete idiot to take doping just before the competition especially such an outdated drug as a steroid, knowing you're going to be tested not once but probably several times."
Ostapchuk also accused Olympic organisers of prejudice against the Belarussian athletes, Reuters reported.
"You all know how we had been treated there, just ask Ivan Tsikhan," she said, referring to the Belarussian hammer thrower booted out of this year's Olympics because of a positive drug test from the 2004 Games in Athens.
"We must fight for our rights. If we remain silent and accept the punishment, then they will continue to humiliate us."
On Tuesday morning, Adams finished second behind Ostapchuk. Her throw of 20.7m was well behind the Belarussian's 21.36m.
Adams was driving to the Switzerland home of her coach Jean-Pierre Egger when she was phoned by New Zealand Olympic chef de mission Dave Currie who broke the news.
"I questioned whether he was telling me fibs or was it really for real. He said 'no, no, no it's for real'. As soon as I hung up from there I got about 26 text messages congratulating me."
She told TV3's Firstline she was "absolutely over the moon".
"Words cannot express how much I am so happy."
However, she admitted she was disappointed she didn't get to stand on the Olympic podium.
"I've been robbed of the moment, so to speak, and enjoying the moment and hearing the national anthem played and just enjoying that with my family being there."
She said she did not want to "waste any of my time or my breath" on Ostapchuk.
"It's a matter of savoring the moment now and celebrating with the rest of New Zealand on what has been, for me, a very emotional last seven days at the Olympics."
Adams' Olympic teammates have rallied behind her.
Gold medal-winning rower Mahe Drysdale told TV3 there had been some suspicions around the Belarussian.
"It's great the system's working, obviously, that everyone's tested and they're finding the drug cheats," he said.
"I still don't think personally, as an athlete, (Adams) will be that happy with her performance because she didn't perform to her high standards but she was still the best clean athlete out there on the day and she was absolutely fantastic.
"All of us as team mates ... are very, very happy to see another New Zealand gold medal."
Ostapchuk, 31, was first tested by urine sample the day before competition and again straight after the final. Both samples showed up the presence of metenolone.
METENOLONE
* A long acting anabolic steroid
* It boosts cellular tissue in muscles and stimulates male characteristics
* It is taken orally or through injection.
