Russian athletes attend a welcome ceremony in Rio de Janeiro on Wednesday. (David Ramos/Getty Images)

When the Opening Ceremonies for the 2016 Rio de Janeiro Olympics arrives Friday night, the 159th out of 207 delegations in the Parade of Nations will enter Maracana Stadium behind a tri-color flag of white, blue and red. It will be carried by a 40-year-old volleyball legend, Sergey Tetyukhin, who is appearing in his sixth Olympics.

But the precise number of Russian athletes in that parade — and on hand for these Summer Games — was a moving target 24 hours before their official opening as individual sports federations were still determining which Russian athletes will be cleared to compete. By Thursday evening, the number of Russian athletes cleared had climbed to 271.

But even as those clearances were being made, evidence was mounting to support the widely held view — among many in the anti-doping and athletes’ rights communities — that the entire Russian delegation should have been barred from the Olympics in the wake of what the World Anti-Doping Agency has described as a vast, state-sponsored doping program across as many as two dozen Olympic sports.

On Thursday morning, the independent, nonprofit investigative website Pro Publica published an interview with the former investigative chief of WADA, who accused his former bosses at the anti-doping watchdog of colluding with Russian authorities and the International Olympic Committee to delay a damning investigative report into the Russian doping program long enough to ensure the IOC and its individual sports federations would not have enough time to ban all of the Russian competitors.

“WADA handed the IOC that excuse by sitting on the allegations for close to a year,” former WADA chief investigator Jack Robertson told Pro Publica. “. . . WADA waited until the 11th hour, only once it was exposed to the public by [leaked media reports] and so the IOC could say there wasn’t enough time.”

In deciding to leave the fates of Russian athletes up to the individual sports rather than imposing a full ban, “The IOC knows there’s simply not enough time for the federations to make a determination. But also, it’s not [the federations’] job. This was not the IOC’s buck to pass,” Robertson said.

Robertson, a former agent with the U.S. Drug Enforcement Administration, laid most of the blame for the mishandling of the doping allegations on WADA President Craig Reedie, who is also a vice president of the IOC and who, according to Robertson, was “more committed to preserving his [Russian] friends’ reputations than discovering the truth.”

Reedie “wanted to avoid an investigation and try to resolve this quietly with the Russians to save them further embarrassment,” Robertson said.

Reedie and WADA have defended the timetable of their investigative report, which wasn’t released publicly until July 18, less than three weeks before the start of the Rio Olympics, by saying the organization moved as quickly as possible once presented with “concrete” evidence of systematic doping. The IOC, meanwhile, has defended its refusal to ban the entire Russian delegation by arguing it would have inevitably punished unfairly some clean athletes. The IOC provides WADA with a large chunk of its funding.

“This is not a [matter] of helping [Russia]. This is a decision of justice, which we could take only on the facts,” IOC President Thomas Bach said at a news conference Thursday. “And this we have done. . . . This is why we have taken measures here against the people being implicated.”

Even though the Russian track and field federation at the center of the doping scandal was officially banned by the sport’s worldwide governing body in June — and the International Weightlifting Federation last week banned Russian lifters under its own rules for multiple doping violations — other sports were still making their final decisions about Russian competitors Thursday afternoon, following reviews of their doping records.

Throughout the day, the updates kept coming: 11 boxers, 11 judo athletes, golfer Maria Verchenova, 30 volleyball and beach volleyball players, five equestrian riders — all cleared by their sports’ governing bodies. In some cases, alternate teams or athletes from other countries were standing by in case of an opposite decision that could have opened up a spot in the competition.

The 271 clearances made official by late Thursday represented about 70 percent of the 389 Russian athletes originally selected by the country to participate in the Olympics, with the bulk of the absentees being track and field athletes.

The bulk of the Russian team arrived Thursday and checked into the Athletes’ Village, and many of them are already undergoing additional drug testing, according to reporters who attended a news conference with Russian Olympic Committee President Alexander Zhukov.

Given the volume of testing to which it has been subjected, Zhukov said, the Russian team “is probably the cleanest in Rio.”