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New York (CNN) -- A venomous Egyptian cobra went missing from New York's Bronx Zoo, prompting the closure of the zoo's reptile house until further notice.

Staff was alerted Saturday that the adolescent Egyptian cobra was missing from an off-exhibit enclosure, according to a statement from the zoo. Staff members closed and secured the reptile house.

Zoo officials said they are confident the 20-inch-long snake is contained in a nonpublic, isolated area of the building.

"Based on our knowledge of the natural history and behavior of snakes, we know they seek closed-in spaces and are not comfortable in open areas," the zoo statement said.

The Egyptian cobra is most commonly found in North Africa. Its venom is so deadly that it can kill a full-grown elephant in three hours -- or a person in about 15 minutes, according to wildlife experts. The venom destroys nerve tissue and causes paralysis and death due to respiratory failure.

Scholars believe the Egyptian cobra was known in ancient times as the asp. Legend has it that Cleopatra, the ancient Egyptian queen, used an asp to commit suicide.