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.

What do we know about the collapse?

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.

Has there been an investigation?

Authorities opened a probe immediately after the collapse, promising it would be thorough and would not spare anyone regardless of position. On Thursday, 11 people were detained.

The suspects, who have not been identified, face charges "of committing criminal acts against public security, causing public danger and irregular conducting of construction work,” the Higher Prosecutor’s Office in Novi Sad said in a statement.

Serbian media reported that Goran Vesic, who resigned as construction minister after the collapse, was among those detained.

Prosecutors said earlier that several dozen people have been questioned. The only information about the investigation so far has come from Serbian media, which published unconfirmed reports about the companies involved in the reconstruction.

Why are people protesting?

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.