A teacher who reported allegations that a co-worker was touching students inappropriately, and was subsequently fired, on Thursday sued the Manhattan preschool where she had worked, saying her termination violated whistle-blower protection laws.

According to the lawsuit filed in State Supreme Court in Manhattan, Mariangela Kefalas, who was hired as an assistant teacher at International Preschools in Midtown Manhattan in September 2012, noticed what she described as the inappropriate behavior of a teaching intern named Malthe Thomsen in late May.

For several days after that, her lawyers have said, she watched Mr. Thomsen and took cellphone videos of him with children on his lap and giving them hugs.

On May 30, the suit states, Ms. Kefalas, 28, wrote an email to her supervisor reporting her concerns about Mr. Thomsen. After conducting an internal investigation of his actions, the school said it had found nothing amiss. On June 5, Ms. Kefalas was fired.