The police fired tear gas to into a crowd of state train operator PT KAI's temporary contract and outsourced workers during a protest to demand promotion and permanent employee status on Tuesday.
The workers, who left their work posts to hold the strike, marched to the office of KAI's subsidiary PT KAI Commuter Jabodetabek (KCJ) at Juanda Station in Central Jakarta.
As no officials were willing to speak with them, the workers tried to break in but faced a police barricade.
The police were still guarding the area as of Tuesday afternoon, kompas.com reported.
Many commuters had to endure long delays to get tickets as most of the ticketing staff were absent. But in Bojonggede Station, Bogor, the commuters were treated a free ride.
"Everything is under control today," KAI spokesperson for the Greater Jakarta operation area, Sukendar Mulya, said.
He said the state firm currently employed 3,000 outsourced workers from eight agencies. "We hope they solve this matter and work together with us to prevent further incidents of this nature," Sukendar said.
KCJ communication manager Eva Chairunnisa said they could only employ outsourced workers as ticket agents and station attendants. "We will discuss this matter with their employment agencies first," she said.