OAK HARBOR, Wash. -- A babysitter accused of preying on young children he met at church pleaded not guilty on Monday despite the partial confession he gave to investigators.

Nathan Martinez, 21, has been charged with 30 sex crimes ranging from child rape to molestation. Martinez admitted to molesting three boys and girls between the ages of 3 and 12 since June 2007. He had been babysitting the children at the time.

But at least 14 alleged victims have come forward, and investigators believe there may be more.

Martinez, who told police he himself had been abused as a child for more than a decade, volunteered as a youth counselor at the Living Faith Christian Center, teaching Sunday school and showing kids how to dance.

Some of the alleged victims could be members of the church, investigators said; however, they do not believe the abuse took place at the church. Martinez did not babysit all of his alleged victims, investigators said.

Island County Prosecutor Gregory Banks said there will be justice.

"I'm sure it just a nightmare and a horrific discovery. I have children. We all want our children to be safe. And all I can say to them is to take care of your kids and at least know they're safe now from Mr. Martinez, because he's behind bars," he said.

Prosecutors said additional charges could follow if more victims come forward.

The investigation began when four of the alleged victims' parents went to the police after hearing three of the children talk about the "nasty things" Martinez had done to them.

Police said Martinez, during a taped interview, said he "knew what he was doing was wrong" and therefore would apologize to the children afterwards. Martinez said he tried to stop several times but the temptations always returned, according to court documents.

Martinez is being held on $250,000 bail.