TACOMA, Wash. -- The Puyallup Police Department said it received multiple tips over the weekend that helped find two girls who were thought to be in "grave danger," but police said they believe other children are at risk.

Police said pictures of the girls were found among pornographic photos on a computer and camera that belonged to Andrew Kowalczyk, who was arrested on Dec. 28 for investigation of identity theft and forgery. Kowalczyk is being held in the Pierce County Jail.

Kowalczyk was charged with four counts of possession of depictions of minors engaged in sexually explicit conduct and is being held on $1 million bail. He pleaded not guilty to the charges.

“It’s very possible that he did in fact manufacture the images, correct. It's an ongoing investigation so facts are unfolding,” Pierce County deputy prosecutor Mary Robnett said.

After the girls' pictures were discovered, Officer Lorri Ericson said, "We're concerned about the children because there are pictures of them in grave danger."

Puyallup police said Monday the girls, who are now 5 years old, were found living safely in a foster home. Their identities have not been confirmed.

Police released four pictures of women, two identified and two who were unidentified, who were thought to know Kowalczyk and may have known the identities and whereabouts of the children.

“It was the tips that led us to find them, it was people who were calling in who helped us make sure these kids were safe,” Ericson said.

"We are still looking for any information that anyone has they have not shared with us yet. We still believe there are other children at risk," Ericson told KIRO 7 Eyewitness News reporter Michelle Millman on Monday.

Ericson said detectives have more than a terabyte of pictures to go through.

"We're not clear how many different children there might be in the picture and what the age ranges might be," Ericson said.

Puyallup police sent detectives to Portland Tuesday to meet with police and members of the Federal Bureau of Investigation in connection with the case that prosecutors said could involve multiple jurisdictions and possible federal crimes because Kowalczyk is believed to have committed several of the offenses under investigation in Oregon and possibly California.

Last spring, KIRO 7 Eyewitness News reported on Kowalczyk after he was caught on camera in Lakewood speeding through a school zone.

Lakewood police found him with a 15-year-old girl in a motel room and arrested him on a warrant out of Oregon.

“Somehow they became aware that he went through a school zone here and got a red flex ticket through the school zone because that was included in the wanted flier,” Lt. David Guttu with Lakewood police said.

Police asked anyone with information about Kowalczyk and the two unidentified women to call 253-841-5421.