Police raided the offices of the Korea Railroad Corporation's labor union in Seoul on Tuesday morning, taking away documents and computer hard drives.
Hundreds of police officers lined up on the streets outside to quell any possible unrest.
Authorities also tried to enforce arrest warrants that were issued on Monday for 10 union members, but they were blocked by crowds of union members from gaining access to them.
The strike has now set a record by going nine days.
It's starting to take a toll on railway services nationwide.
The Korea Railroad Corporation, or KORAIL reduced its operations of KTX express trains by 12 percent on Tuesday for the first time since the strike began.
Subway services were scaled down 7 percent on Monday, directly affecting commuters, who are having to wait longer than usual.
"With the disruption to train services, I was late to my classes and meetings. It's been very annoying."
"Due to the railroad strike, I'm seeing more traffic congestion during the rush hours which is delaying my arrival at work."
"And the prospect of further reductions in the number of KTX and Seoul Metro trains in the coming days raises the possibility for more disruptions for passengers."
Union members of Seoul Metro lines one through four announced that they will join the limited strike starting Wednesday.
The union said it would keep the minimum number of workers on the job needed to keep trains running.
Striking workers are demanding the government reverse its plans to set up a new rail operator, which they claim is a first step toward privatization.
The government and police call it an "illegal strike," and say they will follow the letter of the law in dealing with it.
Shin Se-min, Arirang News.