BELGRADE, Serbia (AP) -- The deadly collapse of a concrete roof at a rail station in Serbia has raised tensions across the Balkan county, fueling widespread anger toward the government and protests after the failure claimed 15 lives in the northern city of Novi Sad.

The station, a major hub, was recently renovated as part of a Serbian-Chinese partnership. Critics allege that corruption, poor oversight and inadequate construction work contributed to the Nov. 1 tragedy. Officials have offered conflicting information about whether the roof was part of the renovation, and its maintenance is under scrutiny.

The collapse became a flashpoint for broader dissatisfaction with Serbia's authoritarian rule, reflecting growing public demands for transparency while the country undertakes large infrastructure projects, mostly with Chinese state companies.

Very little. The rail station was built in 1964 and renovated twice in recent years as part of a wider deal between China, Serbia and Hungary to establish a fast rail connection between Belgrade and Budapest.

Initially, authorities said the outer roof was not renovated during the work on the station, but they gave no explanation for why. Later, experts denied that, and images emerged that suggested at least some roof work was done after all.

One of the protesters' demands has been to make public all documentation in connection with the reconstruction project.

Authorities opened a probe immediately after the collapse, promising it would be thorough and would not spare anyone regardless of position. No arrests have been made, which has added to the public discontent.

Prosecutors have revealed no details, saying only that several dozen people have been questioned. The only information has come from Serbian media, which published unconfirmed reports about the companies involved in the reconstruction.

Responding to calls for arrests, officials said the opposition is after "blood" and on a "witch hunt" and that people cannot be arrested without credible reason. Critics of the government point out that the lack of detentions could lead to tampering with evidence.

In the first days after the tragedy, Serbians protested mostly in silence, holding vigils for the victims. But as time passed, grief gave way to anger, leading to a wave of demonstrations at various locations and by different groups.

Most recently, protesters blocked a courthouse in Novi Sad, demanding that judicial authorities "do their jobs." Riot police pushed them away from the entrance, which led to scuffles and a two-day standoff this week.

Chants such as "corruption kills" also marked the protests that demanded the dissolution of the entire government over the tragedy. Protesters left symbolic handprints in red paint on government buildings, accusing authorities of having "blood on their hands."

Analysts say the government has sought to cushion the damage to its image by prolonging the investigation and apparently hoping that public anger will ease as time goes by.

Serbia's authoritarian president, Aleksandar Vucic, has repeatedly urged calm and called on people to trust institutions. He has said the investigation is complicated and takes time. But Vucic also said that "responsibility cannot be avoided."

At the same time, police detained several activists who took part in recent protests and warned that they would not tolerate any disruptions of public order, which is widely seen as an attempt to discourage people from protesting.

By building roads, railways and other infrastructure, Serbia seeks to enhance its transportation links with neighboring states, while China seeks to strengthen its economic footprint in Europe.

Serbia and China negotiate agreements mostly on a governmental level without the participation of outside bidders. Chinese state banks frequently provide loans to fund those projects. The loans may come with strings attached, such as the mandatory involvement of Chinese companies and their workers.

Although such partnerships have brought billions of dollars in investments into the developing Balkan economy, questions surrounding quality, safety and financial sustainability often remain, as highlighted by the roof collapse.

The Chinese companies that took part in the reconstruction said the concrete canopy that collapsed was not part of their work.

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Associated Press Writer Jovana Gec contributed to this report.