Sandridge Elementary District 172 and law enforcement officials do not know who was responsible for recording sexual activity that took place in a school principal's office -- which is not equipped with security cameras -- or who sent the recordings to parents and the media.

And if the video surveillance tape was made on school property, it was done without the district's authorization, according to a district news release issued Friday morning.

Sandridge Elementary School Principal Leroy Coleman and science teacher Janet Lofton resigned Thursday after DVD recordings began circulating. The DVD shows them having sex in Coleman's office at school.

A third school employee, teacher's aide Anjayla Reed, resigned Friday after District 172 Superintendent Diane Dyer-Dawson contacted her about allegations that she appears on a separate portion of the recording hugging and touching the principal.

Reed gave no reason for her resignation.

Dyer-Dawson said she had not yet seen the DVD recording as of Friday afternoon, although she said one board member had obtained a copy.

School officials have not determined whether the recording was made from inside or outside Coleman's office.

"These resignations do not end the matter as far as the Sandridge School Board is concerned," the release said, issued before Reed submitted her resignation. "The board and superintendent Dr. Diane Dyer-Dawson will be investigating several matters."

These include whether any board members may have known about the presence of the recording prior to it surfacing and how the video recording was made on school property.

Sheriff's Department and South Suburban Major Crimes Task Force officers Thursday night searched the school to look for the camera and other items that may be related to the investigation.

Contrary to televised reports, the FBI was not part of the search at Sandridge Elementary School, Cook County Sheriff's Police Department Deputy Chief John Palcu said.

"At this point (the camera) wasn't found last night," Palcu said Friday morning. "I'm pretty sure it was removed. If it was a setup, they got what they wanted and then distributed the DVDs."

Investigators obtained a copy of the DVD and the envelope it arrived in from a parent who received it.

Investigators were still interviewing people Friday who couldn't be reached the day before. They hoped to interview Lofton on Friday, and several staff members, including the superintendent and the school board president have been interviewed, Palcu said.

Cook County's investigation is also centering on the anonymous source of the DVD, who may have placed the camera and did the recording.

"We're looking at everything and can't close the door on anything," Palcu said. "(The sex) looked consensual. There was not a struggle or anything."

The investigation could be completed by Monday or Tuesday and forwarded to the Cook County state's attorney's office, he said.

-- The Associated Press contributed to this report.