Iranian authorities launched a heavy crackdown on the transit workers late last month, arresting large numbers of bus drivers who had decided to go on strike.
Earlier this month, a dissident worker told Iran Focus that agents of Irans Ministry of Intelligence and Security (MOIS), the countrys secret police, had been conducting night raids into the homes of striking bus drivers and workers in Tehran, arresting more than a thousand people on political charges.
During Mondays protest by the recently released bus drivers, they demanded that the government clarify their position and reinstate them to their previous posts.
Many of the unions members are believed to still be behind bars. Four union activists had to appear in court on Monday.