An inmate who was found unresponsive in his cell at the Fairfax County Adult Detention Center last week died Sunday at a hospital, the county sheriff’s office said.

The inmate was identified by authorities as Sha-Kez Amir Green, 18. No cause of death was given, but police said no signs of foul play were found.

Police said he had been at the detention center since Dec. 18, and was found unresponsive in his cell on July 8. Both police and the sheriff’s office said they are investigating.