A 56-year-old volunteer at a church in Diamond Bar pleaded not guilty Monday to unlawful sex with a teenage girl and molesting her younger sister.

Chee Lim Chook, aka Desmond Chook, was a volunteer at River of Life Community Church when the alleged crimes took place at the church between November 2016 and November 2018, according to the District Attorney's Office.

He is facing two counts each of oral copulation of a minor, sexual penetration of a minor and distributing or showing pornography to a minor, as well as one count of unlawful sexual intercourse -- all felonies -- along with a misdemeanor count of child molesting.

Chook, who's been in custody in lieu of $140,000 bail since his arrest in March, was ordered back to court on Sept. 16, when a date is expected to be set for a preliminary hearing to determine whether there is sufficient evidence to proceed to trial.

The older of the two alleged victims reported on Feb. 21 that she was in a sexual relationship with Chook, according to Lt. Andrew Meyer of the Los Angeles County Sheriff's Special Victims Bureau, who spoke with reporters shortly after Chook's arrest.

"These incidents took place when the victim was just 16 years old and a member of the church,'' Meyer said. "The victim stated that the suspect would have sex with her at the church as well as provide her with pornography to watch.''

Chook faces a maximum sentence of seven years in prison if convicted as charged, according to the D.A.'s office.