Administrators at Stuyvesant High School, in Lower Manhattan, are investigating an apparent case of cheating that may have involved more than 80 students communicating about exams via text message, students said, offering a glimpse of what some called a pervasive cheating problem at one of New York City’s most prestigious public schools.

The principal, Stanley Teitel, confiscated a cellphone from a student during a city language exam on June 18, and found text messages on the phone that suggested students had been sharing information about state Regents exams, Mr. Teitel wrote in a letter to the parents of students who he said were involved.

“I find this breach of integrity very serious,” Mr. Teitel wrote in the letter, which was obtained by The New York Times and which students said was sent to 92 pupils.

City education officials said they were investigating the matter, describing the schools chancellor, Dennis M. Walcott, as “furious.” An official familiar with the matter said the number of students involved was 80, but could rise.