The Jamaica Anti-Doping Commission said the athletes' second samples were tested at a Montreal lab accredited by the World Anti-Doping Agency. It says all five athletes have been notified and the findings will be passed on to the Jamaican Anti-Doping Disciplinary Panel so hearings can be scheduled.
Paul Doyle, the agent for Powell and Simpson, did not immediately respond to a Friday email seeking comment. The athletes and their agent have focused on a new physical trainer, Christopher Xuereb of Canada, saying supplements he provided caused the positive tests.
However, Xuereb has said he didn't give the sprinters performance-enhancing drugs and suggested he was a scapegoat.
Powell and Simpson tested positive for the banned stimulant oxilofrone at Jamaica's national championships in June. Discus throwers Allison Randall and Travis Smikle, along with a junior athlete, also tested positive for prohibited substances at the same meet.
Powell was the last man to hold the 100-meter world record before teammate Usain Bolt broke it in 2008. He also helped the island win the 400-meter relay gold at the 2008 Olympics. Simpson won Olympic gold in the women's 400 relay in 2004 and silver in 2012, along with silver in the 100 in 2008.
The two Jamaican sprinting stars and trainer Xuereb were formally placed under criminal investigation in Italy following a hotel raid in July the northern resort town of Lignano Sabbidadora, where the Jamaicans have been training for years.
This week, an Italian prosecutor said their criminal doping investigation has been delayed because they have been unable to contact the athletes to ask whether they wish to observe the testing of substances sequestered during the police raid.
Meanwhile, a Jamaican disciplinary panel is deliberating a verdict after a four-day closed-door hearing on a positive doping test by another marquee sprinter, three-time Olympic gold medalist Veronica Campbell-Brown. The panel includes a former judge, a former senior military official and the head of the island's medical association.
One of Campbell-Brown's lawyers representing her at the hearing was PJ Patterson, a former prime minister who led Jamaica from 1992-2006 and remains a highly influential figure on the island.
The 31-year-old champion sprinter is the 2004 and 2008 Olympic winner in the 200. She also won gold in the 4x100 relay at the 2004 Athens Games. In London, she won bronze in the 100 and silver as part of the 4x100 relay team. She was suspended from competition in June after testing positive for a banned diuretic at a meet in May in Jamaica, according to a top Jamaican anti-doping official.
But the doping case involving Campbell-Brown appears to involve a "lesser" offense of unintentional use of a banned substance, IAAF spokesman Nick Davies said in June.
The doping positives of three of the island's sprinting stars have staggered many in Jamaica, where track athletes are beloved and global domination in sprinting is a huge source of national pride.
In recent days, Renee Anne Shirley, the former executive of the Jamaica Anti-Doping Commission, has made waves in Jamaica after revealing a number of "troubling" problems during her brief tenure as the top official. She has disclosed that the commission did not have the staff to carry out rigorous anti-doping programs and just one out-of-competition test was done between February 2012 and the start of the London Olympics five months later.
The anti-doping commission has responded defensively, saying it has viewed with "deep concern the utterances by various persons in the public sphere in their attempt to discredit the work of JADCO, its commissioners, the government of Jamaica and the success of Jamaican athletes."
Since starting testing in May 2009, JADCO says it has conducted 876 tests - 504 in-competition and 272 out-of-competition.