The parents of two infants became suspicious of the nanny they hired, so they secretly videotaped her last week, then watched in horror as the recording showed her repeatedly hit, kick and toss the children.

Joan Kahn of Ridgefield, a white-haired 59-year-old with “a great resume and great references according to the father of an 11-month-old Wilton boy, was arrested Friday by Wilton police. She was charged with two counts of risk of injury to a minor, a felony carrying a maximum 10-year sentence. Kahn was set free on $50,000 cash bond shortly after her 11 p.m. arrest. She is to appear Monday in state Superior Court in Norwalk.

The videotape depicts the nanny jerk the children toward her and away from her. At on point, while using harsh language, the nanny is shown lifting a child and slamming him face-down on her thigh. At another point, she throws an empty baby bottle at the head of a child. After seeing the tape, the parents immediately contacted police.

The parents of the Wilton boy, in whose hose the nanny cared for both children, put a hidden camera in the living room last Monday. An excerpt of the video tape, about 10 minutes long, was placed in the court record.

Kahn’s husband yesterday said neither he nor his wife would comment and referred all questions to Kahn’s lawyer, Herbert Rosenberg of Ridgefield, who also refused to comment.

Asked what effect the children’s treatment has had on them, the father said he “can’t answer that.” An arrest warrant application in Kahn’s court file describes her treatment of the children as “potentially harmful physical handling.”

Kahn was hired in October by the parents of the boy and the Fairfield parents of a 10-month-old girl. The mothers of the children knew each other and jointly hired Kahn.

The parents told police they became suspicious when they saw the children’s diapers weren’t changed enough, and when scratches, bruises and gashes started appearing on the children. When the parents questioned Kahn about the marks, she couldn’t give them satisfactory answers, according to police reports.

When police questioned Kahn, she at first denied she ever hurt the children. When they invited her to watch the videotape at the Police Department, she did so, according to police reports.

Watching herself drop the boy three feet onto a pillow on the floor, Kahn said, “I dropped him onto a pillow,” police said. Seeing herself slam the boy’s chest onto her thigh, she said, “Not the best,” and “Not the greatest.”

Police said Kahn told them she was much rougher than she should have been and didn’t remember hitting the children.

“For other people who have nannies, it’s tough to trust them,” the Wilton father said. “I think the videotape is something anyone should consider if they have any suspicions. “The parents got their cameras from a company called “Know Your Nanny,” he said.

The New Jersey-based company performs background checks on nannies and provides parents with cameras hidden in devices such as videocassette recorders, clocks and other working appliances.

The mothers of the two children are taking time off from their jobs to watch the children, the Wilson father said. No arrangements with another care provider have been made yet, he said. The Fairfield parents could not be reached for comment.

“We placed our children in her charge with confidence, and she violated that confidence,” the Wilson father said. “This is an appalling situation we have.”