Chapel Hill, N.C. — Chapel Hill High School officials have been able to connect only four students to a cheating scheme at the high school.

That's according to Stephanie Knott, assistant to the superintendent for community relations for Chapel Hill-Carborro City Schools. Knott said Tuesday that school officials have no evidence to implicate any other students in the scheme.

Knott said she did not have further information about the students involved other than to say they face out-of-school suspension for up to five days and that they received a zero grade on the test in question, which she believes was a social studies mid-term.

Knott also said the cheating should be construed as an isolated event, not as a widespread problem.

"Despite student allegations about events that may have transpired in previous school years, the school and district have been unable to uncover any evidence that they actually took place," Knott said, reading from a written statement.

In an e-mail to parents Thursday, Chapel Hill High Principal Jackie Ellis said officials believe students passed around copies of answers to at least one test that was obtained by using a copy of a master key passed down from student to student through the years.

"The information about it happening for a longer period of time has been forthcoming from the students who were caught in this instance," Knott said.

The student or students allegedly obtained the tests by entering teachers' offices after school, she said. They were captured on the school's surveillance cameras.

Chapel Hill police are not investigating the case, Lt. Kevin Gunter said, and will not be involved unless the school district makes a request.