Brothers Kamiar Alaei and Arash Alaei -- internationally recognized for their revolutionary work in how drug addicts and HIV/AIDS-infected people are treated in Iran -- were taken to an undisclosed location by the authorities in late June.
In an interview with RFE/RL's Radio Farda, the mother of the two men, who did not want her name used, said they are entirely innocent of any wrongdoing.
"They were not [involved] in politics. They worked in the field of AIDS and drug addiction," she said. "They have appeared on Iranian state television many times to talk about these issues.... They have been involved only in scientific work and research."
She said she has no information on their whereabouts.
Read an interview with the Alaei brothers conducted in Washington in 2006 by RFE/RL correspondents Fatemeh Aman and Heather Maher here.
Both men have spoken about the situation with HIV/AIDS in Iran during professional visits to the United States.
Kamiar Alaei, co-founder of Global Health in the Middle East and Central Asia, is a doctoral candidate at the State University of New York at Albany School of Public Health. The Asia Society recognized him as a 2008 Asia Fellow, "one of 23 new fellows identified as being among the most promising trendsetters and emerging leaders in the Asia-Pacific region."
Kamiar reportedly returned to Iran in early June to spend the summer working there.
The two brothers also participated in the Aspen Health Forum in October 2007, a gathering of U.S. and international health leaders organized by the Aspen Institute.