Military police raided the Perth barracks of the elite Special Air Service Regiment in search of drugs last year after one of its members was allegedly busted for ordering a stash of cocaine, ecstasy and LSD from the internet.

The investigation is one of more than 120 launched by military authorities into suspected drug possession, trafficking or involvement with outlaw bikie gangs in the past two years, according to documents seen by The West Australian.

Figures released by the Defence Department show it sacked more than 100 of its members for failing drug tests in the past 18 months. The Australian Defence Force Investigative Service launched a two-month investigation of two SAS members early last year over suspected drug possession and supply.

The investigation is detailed in heavily censored documents released by the Defence Department under Freedom of Information laws, and seen by The West.

It began after WA Police raided a private residence and found drugs, and a phone containing text messages implicating two SAS members “as being involved in the possession and use of illicit substances”.

The documents say text messages on the seized mobile phone show the soldiers also exchanged information on how to beat drug tests. In response, authorities ordered a search of the pair’s work spaces, lockers and cars at Campbell Barracks, seizing more phones, over-the-counter medication and a vial containing “unknown liquid” — which later tested negative for drugs.

Investigators also sought permission to search their defence-subsidised rental accommodation.

One soldier agreed, the second refused.

But despite what investigators described as “extensive inquiries” the searches yielded no evidence of involvement in drugs for either man, and the records show the investigation was dropped by military authorities and referred to the SAS for internal disciplinary action. The Defence Department yesterday did not respond to a request for comment on the action it took against the men, and the outcome of the WA Police investigation is also unclear.

A spokesman said the ADF did not tolerate the use of illicit substances, or involvement in the possession or supply of prohibited substances.

Each year a quarter of ADF personnel are subject to random or targeted urine tests for drugs.

The testing program has been expanded to include hair and saliva testing on a trial basis.

More than 29,000 tests have been conducted since July last year, yielding 183 positive results. Of those, 100 servicemen and women were sacked as a result.