The brothers have become the first to be sanctioned as a result of the probe after website owner Josh Townshend was jailed for two years for advertising, possessing and supplying banned substances.

A database collected by Townshend, who ran the Clenbuterol NZ website, contains the names of around 100 athletes who used the service between 2014 and 2015.

It was initially thought that there were not any elite-level players on the list.

New Zealand Rugby Players' Association head Rob Nicol told Radio New Zealand, however, that they were supporting one athlete, who was not playing at the time.

Drug Free Sport New Zealand (DFSNZ) has begun investigating the database and has initiated disciplinary proceedings against those involved.

"To have identified approximately 100 athletes using a website selling these substances is extremely disappointing to us at DFSNZ, and should also be of great concern to the wider sporting community," DFSNZ chief executive Nick Paterson said.

"It’s been previously stated that few, if any, of the prohibited substances available for purchase on the Clenbuterol NZ website were of pharmaceutical grade.

"Who knows what people were consuming or injecting themselves with."

"We have now invested in our intelligence and investigation capability and, coupled with the advances in science, drug cheats are going to find it harder and harder to go under the radar."

DFSNZ imposed the two-year sanctions on Mitchell and Lachlan Frear despite admitting there was little evidence they had taken the banned substance they had bought over the internet.

Both argued that they never received clenbuterol.

The brothers said they had bought the substance as it was advertised as a fat-burner.

DFSNZ ruled, however, that they were guilty of attempting to procure a substance on the prohibited list.

Their respective suspensions have been backdated to January 1 of this year.