TEHERAN - Three Americans detained in Iran on the charges of espionage are to stand trial on May 11, local ISNA news agency reported Monday.

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Massoud Shafiei, the lawyer of the three US nationals, told ISNA that "A citation was issued for me stressing my presence in the trial session."

Shafiei said Iranian Foreign Ministry has issued summons for Sarah Shourd, one of the three who was released last year, to appear in the court.

The female hiker Shourd, once jailed in Iran with the other two Americans, was released by Teheran's prosecutor in September on a bail of $500,000.

In February, an Iranian court held a close-door trial of three detained Americans Josh Fattal, Shane Bauer and Sarah Shourd, who were arrested in Iran on July 31, 2009 for illegally entering Iran's western border and were later charged with espionage. The US government considered the charges totally unfounded.