At least two children were among those killed in the disaster, which happened on Friday when a length of roofing along the entrance to the station collapsed on a sunny day.
The station in the city about 70 km northwest of Belgrade underwent renovations in 2021 and 2022. Other minor works continued until July this year when the Transport Ministry said a total of €16 million had been invested in the renovation.
Transport Minister Goran Vesic said on Saturday the inquiry, opened by prosecutors in Novi Sad, would include the state Traffic Institute, state railway company and the Chinese consortium that undertook the renovation work.
"The investigation will determine ... who made decisions and put seals and signatures, who was in charge of controlling the (quality of) works," Vesic said in a TV broadcast.
Vesic, state Serbian Railways company, the state Traffic Institute and the Chinese consortium - China Railway International and China Communications Construction Company, that renovated the building, all said on Friday that the part of the building that collapsed was not a part of the works.
Interior Minister Ivica Dacic said 20 people would be interviewed by authorities on Saturday in connection with the disaster, including people from the ministry in charge and the state railways operator.
"The documentation about the building will (also) be obtained ... about who made the decisions," Dacic added.
Authorities declared Saturday a national day of mourning.
Serbia's opposition, which accuses authorities loyal to President Aleksandar Vucic of rampant corruption, nepotism and excessive red tape, called for a protest in downtown Novi Sad later in the day.
In a televised address, President Vucic promised justice, demanding harsh punishment for those responsible.
