"There's a secret director," Fey said.
She was speaking at Produced By: New York, an annual east coast conference held by the Producers Guild of America, reported Entertainment Weekly.
Fey also gave out other details of the project she has been developing with her husband, composer Jeff Raymond.
"We're assisting Nell Benjamin, he's doing the lyrics this time".
The musical is scheduled to debut in Washington, DC in 2017.
"Mean Girls" was released by Paramount in 2007, and went on to gross nearly USD 130 million worldwide.
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