ALHAMBRA — Prosecutors Thursday filed new charges of possession of child pornography against a Walnut man awaiting trial on accusations that he bound and attempted to rape and kill a female employee of his at a Monterey Park yogurt shop he owned, authorities said.

Robert Yachen Lee, 37, was free on bond as he awaited trial for on suspicion of kidnapping for the purpose of rape and attempted murder in connection with the alleged attack, which took place Aug. 24.

But Lee was re-arrested Thursday when he appeared in Alhambra Superior Court for a pretrial hearing after officials amended the felony complaint against him to include a count of felony possession of child pornography.

“They were on his personal computer,” Monterey Park police Lt. Carrie Mazelin said. “It was in his possession when we arrested him (in August).”

The images were discovered in recent weeks during a forensic search of Lee’s computer with the help of Los Angeles County Sheriff’s investigators, officials added.

Though the computer was seized following Lee’s initial arrest, the lieutenant said, it can take months to complete a forensic search of a computer.

After the complaint was amended to include the new charge, Lee was taken back into custody by sheriff’s deputies and bail was set at $5 million, Mazelin said.

The identity of the children depicted in the pornographic images found on Lee’s computer was not known, Mazelin said. Detectives were looking into whether they were images that had been sent to Lee from someone else, or if he may have been involved in creating them.

In the initial assault at O My Yogurt, in the 2200 block of South Altantic Boulevard in Monterey Park, the young woman escaped captivity and sought help from a nearby business, officials said.

“Lee attacked the woman from behind (Aug. 24) after luring her to an upstairs storage room,” Los Angeles County District Attorney’s spokeswoman Sandi Gibbons said in a written statement.

Lee overpowered the woman and bound her with tape and placed her into, “what appeared to be a soundproofed box and placed into a recently padded and soundproofed room that was part of the storage suite,” Gibbons said.

Police and district attorney’s officials said the woman managed to free herself from the box she had been locked in, fled to a nearby optometry office and asked someone to call the police.

“She definitely saved her own life,” Mazelin said.

Police arrested Lee about two hours later.

Lee was ordered to return to court June 21 for a preliminary hearing setting, court officials said.

If convicted as charged, Lee could face life in prison without the possibility of parole.

PHOTO of Robert Yachen Lee, 37, of Walnut courtesy of the Monterey Park Police Department