* Colombian Palomeque tests positive for testosterone
* IAAF confirms two more cases
* Athletes back on Olympic track after bans (Updates with IAAF confirmation on two more cases)
By Karolos Grohmann
LONDON, Aug 4 Doping moved back into the spotlight at the London Olympics on Saturday with at least four more confirmed positive cases and a string of high-profile doping offenders returning to the world's biggest sports stage in search of restitution.
On the day when athletics, the flagship sport of the Games, took centre stage with its big names starting their quest for gold, Colombian 400 metres runner Diego Palomeque Echevarria became the latest athlete to be banned following a positive first test for performance-boosting testosterone.
Scheduled to run on Saturday morning, he was temporarily suspended pending a B sample test, the International Olympic Committee (IOC) said on Saturday.
He joined Russian cyclist Victoria Baranova, who was sent home for failing a test for testosterone, to bring the tally of athletes suspended by the IOC to four since the start of the Olympic period on July 16.
Belarussian hammer thrower Ivan Tsikhan and Moroccan runner Amine Laalou were also ruled out with the International Association of Athletics Federations (IAAF) saying they had been charged with anti-doping rule violations.
Tsikhan won the bronze medal in Beijing four years ago but was stripped of it after testing positive for testosterone.
"The IAAF is now in a position to confirm that Ivan Tsikhan and Amine Laalou have both been charged with anti-doping rule violations under IAAF Rules."
"Each athlete has been provisionally suspended by the IAAF pending the outcome of a hearing before the relevant disciplinary tribunal of his respective federation," it said in a statement.
Several other athletes, including Brazilian rower Kissya Cataldo da Costa who was expelled on Saturday for failing a dope test for EPO, have been sent home by their own federations.
"I do not think this changes where we are at all," IOC spokesman Mark Adams told reporters, when asked whether the latest positive tests were showing a wider use of banned substances at the Games than expected.
"Cheats are being caught and ejected," he said. "At this stage it is a pretty low number."
Ironically, it was also the day when former big name doping offenders Justin Gatlin, Dwain Chambers and LaShawn Merritt made their Games comebacks in front of an enthusiastic 80,000 crowd.
"I would clearly rather have that these competitors are not here," Games chief Sebastian Coe told Reuters.
"The federation says they are eligible to compete, the IOC says they are eligible to compete so we give them as much courtesy as all the other athletes.
"The answer is that that is the world we live in," said Coe who added that he wanted to have a four-year ban for first time offenders rather than the current two years.
"I am sorry my sport has moved from four to two years," the former twice Olympic 1,500 metres champion said. "I don't think that this is a sufficient deterrent."
Briton Chambers, once the face of doping, needed a British lifetime ban for drugs offenders to be overruled so he could run at the Olympics.
While his comeback after suspension a few years ago was greeted by jeers and boos, he received a raucous welcome from the home crowd at the Games where he won his heat in 10.02 seconds.
"More than anything, it's just a great feeling to know that when you've had upsets in your life, if you still remain focused and believe in yourself anything can happen," he said after winning his heat in style.
Gatlin, the 2004 Games 100 metre gold medallist, and back for his first Olympics after serving a four-year doping ban, was even more dazzling with a time of 9.97 seconds in the second heat of the first round.
"I had a couple of tears before I got on the track," he said. "It's good to be back."
Merritt, the 2008 Olympic champion in the 400 metres, also made his comeback on Saturday. He was less fortunate though, dropping out of his title defence after only a few seconds due to a hamstring injury picked up last month.
He served a 21-month drugs suspension for using of an over-the-counter male enhancement product in 2010 that contained the banned substance dehydroepiandrosterone (DHEA) and pregnenolone.
There was no intention to dope nor to gain a competitive advantage, an international panel found. (Editing by Alison Williams)