A former Serbian government minister and 10 others were arrested Thursday over the deadly collapse of a train station roof three weeks ago in which 15 people died.
The tragedy in the northern city of Novi Sad earlier this month has fuelled a wave of anger in the Balkan nation, with many blaming the deaths on rampant corruption and lax oversight of construction projects.
The collapse came after years of renovation work on the station.
Prosecutors said 11 people had been arrested including a former construction minister.
But Goran Vesic, who resigned three days after the November 1 collapse, denied he had been held, writing on Facebook that he had "voluntarily responded" to police.
Trade Minister Tomislav Momirovic, who was construction minister when work began on the station, was also forced to resign on Wednesday.
The opposition welcomed the arrests but protesters are demanding that the prime minister and the mayor of Novi Sad also quit, along with the prosecution of officials responsible for the tragedy.
Doctors are still fighting to save the lives of two of the mostly badly injured victims.
The Novi Sad prosecutor's office said it has questioned over 70 people since the tragedy, but no arrests were made until Thursday morning, sparking criticism from the opposition, which has been demanding a faster investigation.
Opposition MPs have been blocking the entrance to the prosecutor's office in Novi Sad for the last three days, occasionally scuffling with the police.
"Pressure and persistence have succeeded," wrote opposition MP Marinika Tepic on X.
"I am certain these arrests would not have happened if we had not been so persistent. However, we are not satisfied with the charges being brought against them," Tepic said, with the blockade of the prosecutor's office still ongoing.
The protestors have also demanded the publication of the contracts signed with the companies involved in renovating the station.
A consortium of four companies -- China Railway International, China Communications Construction, France's Egis and Hungary's Utiber -- were in charge of the works.
The opposition Green-Left Front hailed the arrests.
"Those who portrayed themselves as untouchable (are) now trembling before justice, thanks to the pressure from citizens, the opposition, protests, and blockades. If Vesic can be held accountable, anyone can -- citizen pressure brings change," the party said.
Serbian President Aleksandar Vucic did not comment on the arrests but said that authorities had been subjected to "terror" for days to "supposedly speed up the work of the Prosecutor's Office."
"Our Prosecutor's Office has made decisions 100 times faster than in developed EU countries when similar incidents occurred," Vucic said in a video message on social media, promising further comments later in the day during his appearance on national television.
