The four are editor in chief Ahmad Gholami; international section editor Farzaneh Roustaei; Keyvan Mehregan, a member of the political team; and financial manager Ali Khodabakhsh.
The Iranian authorities have not yet made public the charges against them.
A Tehran-based journalist who did not want to be identified tells Radio Farda the December 7 arrests may be related to a special edition of "Sharq" published that day to coincide with National Student Day.
That issue, titled "The Student Movement is Alive," contained articles and interviews by critics of the government focusing on the state of the student movement in Iran.
Students staged antigovernment rallies on December 7 at several universities, including Tehran University, Amir Kabir University, Gilan University in northern Iran, and the University of Sistan and Baluchistan in southeastern Iran.
One of the most popular reformist dailies in Iran, "Sharq" has been banned three times since its first publication in August 2003.
The paper resumed publication in April 2010 after a 2 1/2-year ban.
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