A principal and a teacher at a suburban Chicago elementary school quit amid allegations they were caught on video having sex in the principal's office, authorities say.

In keeping with Cook County's reputation for bare-knuckle politics, the scandal broke after copies of the sex tape were mailed anonymously to parents this week, just days before a contested school board election.

The case has also created something of a mystery: Who planted the camera that recorded the action?

Leroy Coleman and Janet Lofton submitted their resignations after meeting with the district superintendent Thursday, said John Izzo, board attorney for the Sandridge Elementary School district, about 20 miles south of Chicago.

Izzo said that Coleman, the school's principal since 2005, wrote that he was quitting for health reasons. He said Lofton wrote that she was stepping down immediately "due to the illness of a family member."

A third school employee, teacher's aide Anjayla Reed, resigned Friday after the superintendent contacted her about allegations that she appears on a separate portion of the tape hugging and touching the principal, Izzo said. She gave no reason for her resignation.

Kim Grivakis, the mother of a 13-year-old girl and 11-year-old boy who attend the school, said she received a copy of the 2 1/2-hour DVD in the mail Wednesday. She organized a meeting Thursday with other parents to call for action from the school board.

Grivakis said she could identify Coleman, Lofton and Reed on the tape.

"It made me sick," Grivakis said. "It's very graphic. I can't tell you how graphic because I have two children standing right here."

A copy of the DVD viewed by The Associated Press shows a man and a woman hugging, kissing and engaged in various sex acts inside an office. A separate portion of the tape, apparently from a different time, shows another woman hugging and touching the same man.

The Cook County Sheriff's Department is investigating.

"At this point we don't know if a crime has been committed," department spokeswoman Penny Mateck said, adding that investigators had a copy of the video.

Lofton has an unlisted telephone number, and no listing could be found for Coleman or Reed.

Izzo said that that he had been told by a sheriff's official that Coleman and Lofton are on the tape. "They asked to look at pictures of the staff members and they identified them," he said of the investigators.

The school board attorney said Coleman and Lofton apparently did not know about the camera. "Somebody got access and planted a bug in a school office," Izzo said.

He said sheriff's investigators searched the office on Thursday and apparently did not find a camera.

Copies the video, apparently taped in December and January from the date stamps on it, emerged just days before Tuesday's elections. Eight candidates are competing for four board slots.

"How come it took five days before the election?" said school board President Cheryl Ward said. "I think that is sick."