Hundreds of members of the Muslim Brotherhood, including former President Mohamed Morsi, are detained. Morsi was ousted by the military July 3.
Marianne Gasser, head of the Red Cross delegation in Cairo, said the organization hadn't visited with any of the detainees.
"We are not currently visiting detainees in Egypt," she said in a statement Friday. "We do not have precise figures but, according to public reports, hundreds of people have been arrested and detained over the past few weeks, which is a matter of concern to us."
The Red Cross frequently meets with detainees and prisoners of war to verify their health status and exchange family letters.
Gasser said the national security situation in Egypt was a concern for the relief organization. Hundreds of people were killed in clashes between security forces and Morsi's supporters last month.
She said the Red Cross didn't have medical personnel in Egypt at the time of the clashes.
"At the height of the incidents, our main concern was that everyone involved in the clashes should show respect for human life and dignity," she said.