Pishchalnikova, who finished second at the London Olympics this year, tested positive for an anabolic steroid.
"In October 2012, the World Anti-Doping Agency (WADA) ordered that Pishchalnikova's sample, taken on May 20 2012, was re-tested at a laboratory in Lausanne. The result was adverse," RUSADA said in a statement on its website (www.rusada.ru).
"Currently, the IAAF is investigating a possible breach of anti-doping regulations by Pishchalnikova."
RUSADA executive director Nikita Kamayev has confirmed the positive test.
Pishchalnikova, who has denied any wrongdoing, could face a life ban from the sport if found guilty because it would be her second offence. She served a doping ban of two years nine months from July 2008 to April 2011.
The 27-year-old was among seven leading female Russian athletes found guilty of manipulating drug samples before the 2008 Beijing Olympics.
She also won silver at the 2009 world championships in Osaka, Japan, but was stripped of the medal after the IAAF annulled all her results from May 2007.