Urine tests had also returned positive for the drug.
His lawyer Craig Tuck confirmed his client was at the centre of fresh drug allegations but said he had had no contact because prison authorities had confiscated his phone.
De Malmanche is into the second year of his sentence after he was found guilty of drug trafficking in June 2015.
During his trial prosecutors wanted 18 years' jail for de Malmanche, arguing his passport, plane ticket and a Customs declaration form in the same bag as the drugs were enough to prove ownership.
His defence claimed he was a victim of trafficking, rather than a trafficker, and called experts to testify about his mental illness, low IQ and vulnerability to brainwashing by online scammers.