Police have arrested 33 people during protests on the metro system in the Venezuelan capital, Caracas.
They said they were protesting about the poor service of the underground network, which commuter groups say has deteriorated rapidly in recent months.
Police said the passengers prevented a train from leaving a station, and accused them of sabotage.
Last month, the government appointed a new head of the metro system to try to tackle the network's problems.
The arrests were the culmination of several weeks of growing anger among commuters in Caracas over the state of the metro system.
A lawyer acting for the protesters said they were simply angry at having to wait around 40 minutes for a train, only to be told that they could not board the one which eventually arrived.
The police say members of the public refused to let the train leave the station, holding up services on other lines.
The transport ministry accused the protesters of sabotage - something their lawyer has denied.
As the police arrived in numbers at the station in the west of the capital, the protests turned ugly and the arrests were made.
The metro system in the Venezuelan capital was once the envy of Latin America.
However in recent months it seems to have reached saturation point.
Long delays are a daily problem and many trains, escalators and lines are in need of urgent maintenance.
President Hugo Chavez recently appointed a new head of the metro system, which carries some 1.3m commuters a day - the second highest volume in Latin America.
The system was only designed to carry around 600,000 passengers a day.