The fire started Sunday in a wooded area at the zoo and spread to the animal food warehouse, al-Ahram reported.
Reporters from the el-Badil, al-Tahrir, al-Youm el-Sabe and el-Wady newspapers alleged that they were hit by security guards and prevented from entering the zoo.
The reporters alleged the guards threatened to break their cameras.
Al-Ahram said the fire was caused by a cigarette discarded by a visitor.
Crews with six fire engines extinguished the fire, officials said.