Wests Tigers utility Josh Reynolds is awaiting the result of a third drugs test after being pulled over by police while driving home from Bankstown Airport on Monday morning.
Reynolds, who was issued with an infringement for driving with an expired licence, failed a roadside drugs test at Caringbah but a second test was negative.
A further test conducted at Sutherland Police Station has been sent to a laboratory.
The former NSW Origin five-eighth has not been charged with any drugs offence at this point.
Tigers officials advised the NRL of the incident and the integrity unit is working with police.
An NRL spokesman said: "The Wests Tigers advised the NRL Integrity Unit of the matter. The Integrity Unit are working with the club and NSW Police to determine the full details."
Reynolds has posted on Twitter to say: "I arrived back from QLD with the team via plane, late last night. I was driving home to get some food and was pulled up with an expired drivers licence, which I was unaware of and an oversight by me. The officer conducted alcohol and drug testing. The alcohol test was negative.
"The roadside drug test was a false positive. I went to the police station and undertook the further sample for the higher level testing, which proved negative. I am told false positives on roadside tests are not uncommon. I was then released without charge."
The Wests Tigers issued a statement on Monday afternoon to say the club was aware of the incident and working with the NRL Integrity Unit to investigate the matter.
"After arriving back from Queensland at 12:50am as part of the club’s Round 4 squad that faced the Gold Coast Titans on Sunday night, Josh was pulled over by police a short time after for driving without a valid driver's licence.
"Josh underwent roadside alcohol and drug testing, and was taken to Sutherland Police Station for a higher-level test as per normal protocols. This test returned a negative result and Josh was subsequently released without charge."