LISBON, Portugal — Portuguese road champion Joao Cabreira has been suspended for two years by his country's cycling federation after allegedly using a masking substance to tamper with a doping control.

Cabreira was accused of using a substance called protease and has been sanctioned "for tampering with a doping control sample," the Portuguese Cycling Federation said in a statement released Friday to state news agency Lusa.

The 26 year-old former LA-MSS rider told Lusa in a telephone interview that he is innocent and is not familiar with protease.

"I'm innocent. I didn't commit any kind of illegal action," Cabreira is quoted as saying in sports daily Mais Futebol. "I don't know what this substance is, I've never heard of it nor seen it in all my life."

Portugal's anti-doping laboratory suspected there was something wrong with Cabreira's samples and sent them for detailed analysis in Cologne, Germany, where protease was detected.

"The use of protease to manipulate and mask control samples has been known about for quite a long time," said Luis Horta, director of the Portuguese laboratory.

Horta said that protease is an enzyme found in some detergents which use it to degrade proteins.

Anti-doping authorities have suspected some athletes of masking EPO through the use of protease since 2006 when laboratories detected that some riders' samples lacked normal traces of the body's EPO molecules.

Cabreira is the first to be suspended for using protease enzyme to break down EPO in urine to cheat doping controls.