SPOKANE, Wash. -

FBI agents continue their investigation into Matthew Buquet, the suspect who allegedly sent threatening letters with ricin on them to the Spokane Post Office, sifting through everything they retrieved from his residence Saturday morning.

So far, the FBI has had no comment on the ongoing investigation or what evidence they've collected on Buquet, 38, who is facing one charge of mailing threatening communications.

This wasn't Buquet's first brush with the criminal justice system. In 1988 Buquet molested his girlfriend's 10-year-old mentally disabled daughter. When confronted he claimed she instigated the relationship even though Buquet was 22 at the time.

He was sentenced to 18 months in prison for indecent liberties.

Buquet listed on his Facebook profile ABM Industries as his workplace since 1999. The janitorial service released a statement saying Buquet hasn't worked there "in more than a month, long before these letters were postmarked."

KXLY sources say the threat at Fairchild Air Force Base Tursday morning that resulted in the commissary being evacuated was related to the ricin case. Base public affairs officers would neither confirm nor deny the threat was made by Buquet.

Buquet faces one charge of mailing threatening communication so far. The indictment states he threatened to kill Federal Judge Fred Van Sickle. It's not known why Buquet may have sent that message to Van Sickle or what the threat was.

His next court appearance is a bail hearing, which is scheduled for next Tuesday.