Osanlu's wife, Parvaneh Osanlu, said security forces are surrounding their home in Tehran. Members of the union were planning to hold a protest outside the house to call for the release of Osanlu and another jailed union activist, Mahmud Salehi.
The planned gathering was part of a worldwide day of action to free the two men, called by the International Confederation of Free Trade Unions.
In an interview with Radio Farda today, the head of the International Transport Federation, David Cockroft, said the organization is "shocked and angered" by the "outrageous and unnecessary action" taken against Osanlu and Salehi.
Cockroft said the detention of the activists is "unnecessary and provocative harassment [of] people who are doing the simple job of defending the rights of trade union members in important parts of the Iranian economy."