The Secret Service confirmed Thursday Rafael Prieto's death was being investigated by Washington police and the medical examiner's office and that no official determination of death has been made, CNN reported.
His body was found Saturday.
Authorities were looking into Prieto's long-term and apparently unreported relationship with a Mexican woman, a law enforcement official said.
Prieto's access to Secret Service facilities had been suspended while authorities were looking into the 48-year-old's relationship with the woman, CNN said.
"There is nothing to indicate that any classified or sensitive information was compromised as a result of this relationship," an official said.
"Rafael Prieto had a distinguished 20-year career with the Secret Service that was marked by accomplishment, dedication and friendships," Secret Service spokesman Ed Donovan said in a statement. "The Secret Service is mourning the loss of a valued colleague."
ABC News said there was no criminal investigation into Prieto and he was not under investigation for espionage.
Law enforcement officials said there were no indications he passed along sensitive documents.