Griner's attorney, Alexander Boikov, revealed to the news organization that the extension may indicate that her case will head to trial soon.
The WNBA star has been detained in Russia since February when customs officials at an airport outside of Moscow claimed Griner was smuggling vape cartridges containing cannabis oil in her carry-on luggage. The charges carry a maximum sentence of 10 years in prison.
Last month, the US Department of State reclassified Griner as being a "wrongfully detained" American citizen in Russia. At the time, the State Department also announced the successful release of another American detainee, Trevor Reed, who'd been detained in Russia for nearly three years.
Efforts to get Griner released have been ongoing, State Department officials said.