The NRL released a statement on Tuesday afternoon, confirming Xerri had been provisionally suspended from the competition.
"The National Rugby League (NRL) has today provisionally suspended Cronulla Sharks player Bronson Xerri under the NRL's Anti-Doping Policy," the statement read.
"The Provisional Suspension Notice asserts that Mr Xerri returned a positive A-sample for exogenous Testosterone, Androsterone, Etiocholanolone and 5b-androstane-3a,17b-diol which are prohibited by the World Anti-Doping Agency (WADA) and the NRL's Anti-Doping Policy.
"He was tested by the Australian Sports Anti-Doping Authority (ASADA) on 25 November 2019.
"Mr Xerri is prohibited from participating in any WADA compliant sport, including rugby league, while the provisional suspension is in place.
"Under the Anti-Doping Policy, Mr Xerri now has the opportunity to have his B-sample analysed.
"The NRL has spoken with Mr Xerri and advised him of the support services available to him."
The Sharks also released a statement on Tuesday, revealing Bronson had been stood down from training ahead of their round three game against the West Tigers on Sunday.
"The Sharks have today been made aware of the provisional suspension handed down to Bronson Xerri under the NRL's Anti-Doping Policy," the statement read.
"Details of that provisional suspension and alleged breach of the anti-doping policy will be outlined in an NRL Media statement to be distributed today.
"Bronson has been stood down from training and playing responsibilities while the process runs its course, which under the policy includes the opportunity to have his B-sample analysed.
"The Club has been in contact with Bronson and has offered him full welfare support as he deals with this situation.
"The Sharks will be making no further comment on the matter."
Xerri made his debut for the Sharks in 2019, and scored 13 tries in 22 games last season. The star centre did not feature in the opening two rounds of the 2020 premiership due to injury, but was expected to make his return this weekend.