"We are now learning of serious irregularities at this facility that are deeply concerning and demand a thorough investigation", Barr said. "The FBI and the Office of the Inspector General are doing just that. We will get to the bottom of what happened and there will be accountability".
Barr said that he was appalled and angry when he learned of the Metropolitan Correctional Centre's failure to adequately secure Epstein.
The US Attorney General further said that the case will continue on against anyone who was complicit with Epstein in the alleged sex trafficking crimes.
"Any co-conspirators should not rest easy", Barr said. "The victims deserve justice and they will get it".
The statement comes after media, citing law enforcement officers, reported on 10 August that Epstein apparently committed suicide at the prison where he had been held ahead of his pending trial on charges of sex trafficking of minors.
Police have been probing Epstein since the 2000s and detained him in 2005 for molesting an underage girl. Epstein served 13 months in custody.
In July 2019, Epstein was arrested a second time for allegedly trafficking minor girls at his mansion for sex. Some of the charges dated back to the 2000s.
Epstein pleaded not guilty to all charges against him but faced up to 45 years in prison had he been convicted.