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(CNN) -- Days after the world of athletics was hit by serious doping allegations, the sport has been accused of covering up how it dealt with scores of suspicious blood samples.

In the two years between 2006 and 2008, the body in charge of global athletics failed to examine as many as 150 samples from several countries, according to a report broadcast by a German network Monday.

This was a period before widespread changes were introduced to anti-doping procedures.

The allegations reported by German TV station WDR came less than a week after German broadcaster ZDF/ARD aired an hour-long programme documenting Russia's alleged endemic use of banned substances. As with last week's documentary, WDR released an English transcript after airing the report.

The International Association of Athletics Federations (IAAF) is now investigating those claims, but the governing body now finds itself under the microscope.

During Monday's edition of the "Sport Inside," a former member of the IAAF's medical commission -- who is not identified -- said the samples in question were from athletes representing Spain, Kenya, Greece, Germany, Morocco, Russia and at least one from Britain.

"Just take a look the haemoglobin values -- how they have risen in only four months by 38% and in the next four months they have fallen again by 16%", the official explains, according to the English translation of the documentary provided by the broadcaster to CNN.

"It's obvious that there's something wrong there. That simply cannot be. It is absolutely clear to see and physiologically simply cannot be explained. This can only be doping."

President of Spain's athletics federation Jose Maria Odriozola said his organization received no notification of any suspicious samples from the IAAF.

"When we receive information of that type, we immediately carry out surprise doping tests on the suspicious athletes," Odriozola said in an email sent to CNN.

He also outlined that Spanish track athletes are required to supply their "blood passport" -- a method used to monitor any potential doping violations -- a week before competition.

Both British Athletics and UK Anti-Doping have declined to comment, while both the Russian Athletics Federation and Russian Anti-Doping Agency have so far failed to reply to CNN's request for comment.

The IAAF insisted Tuesday that the English transcript of the documentary would be passed on directly to its independent ethics commission.

It also said that "a member of the IAAF Medical and Anti-Doping Commission would not know whether follow-up tests would have been conducted or not."

The athlete biological passport program was launched in 2009, ensuring athlete's blood samples were stored electronically and monitored over time, according to the IAAF.

Samples collected prior to 2009, according to the IAAF, "do not have the same level of reliability and strength as the post-2009 values which were collected under strict and stringent conditions."

The governing body also stated that any samples taken before 2009 were only used as "secondary evidence," or to arrange "trigger" follow-up urine tests.

The IAAF also insists that "abnormal results were duly followed-up by the IAAF, whenever possible logistically."

WADA, the world's anti-doping agency, said it would investigate the allegations in a statement released on Tuesday.

Last week's "Das Erste" documentary had already alleged systematic doping in Russian athletics. It claimed Russian officials covered up positive results in exchange for financial reward.

The Russian Anti-Doping Agency (RUSADA,) announced it would investigate the allegations, while the president of the country's athletics federation told Reuters the claims were "a pack of lies."