Chelsea Manning, who has been incarcerated for declining to testify before a grand jury, has been held in solitary confinement for over two weeks, the US Army whistleblower's supporters say, according to The Guardian.

"We condemn the solitary confinement that Chelsea Manning has been subjected to during her incarceration at William G. Truesdale adult detention center," a committee of supporters said in a statement.

READ MORE: Chelsea Manning Claims She Was Illegally Spied on Prior to WikiLeaks Subpoena

According to supporters group, Chelsea Manning has been kept in a cell for 22 hours a day, which could affect the former army specialist's mental health.

"Chelsea can't be out of her cell while any other prisoners are out, so she cannot talk to other people, or visit the law library, and has no access to books or reading material. She has not been outside for 16 days," they added.

Earlier this month, Manning was arrested following a federal judge's finding that the whistleblower was in contempt of court for rejecting to respond to questions before a secret grand jury.

Manning, formerly known as Bradley Manning, was released from a US prison in May 2017 after serving seven years of a 35-year prison sentence for handing over internal documents to WikiLeaks. The sentence was commuted by then-US President Barack Obama in 2017 as one of his last official acts.