The Austrian blood transfusion specialist Humanplasma, already at the centre of a huge doping scandal, on Friday admitted tax evasion.
Officials for the lab admitted not declaring 300,000 euros earned from taking blood tests from athletes but continued to deny accusations of being involved in doping.
"We have informed the authorities for several months," said lab spokeswoman Michaela Eisler. "The blood tests were simply stocked on lab premises. There were no transfusions."
Humanplasma stressed that the sum concerned blood tests taken between the end of 2003 and early 2006 on some 30 athletes.
Prosecutors opened an investigation at the end of September.
"We want to ascertain whether the revenues from transfusions were included in the accounts and declared to the tax authorities," prosecutor Gerhard Jarosch told AFP. "We've been investigating two people for a number of weeks now. Others may also be involved."
According to the magazine Sportwoche, clients of the lab were from seven countries and six disciplines, and included ten cyclists and four rowers.
"About 150 'treatments' were carried out," a representative of the prosecutor's office said.
Eisler said the lab "had the task of taking these blood tests to ensure 'equal chances' for Austrian athletes".
To date only cyclist Bernhard Kohl, stripped of his third place finish in the 2008 Tour de France for doping, has admitted being a client of Humanplasma.
Kohl said he had gone to Humanplasma for transfusions with blood supplied by his former manager Stefan Matschiner.
Matschiner, who admitted to performing irregular blood transfusions for Kohl, is accused of organising a doping network which helped top athletes in Europe to cheat by using performance-enhancing drugs and methods.
© 2009 AFP