Three state railway employees have been detained in Turkey on suspicion of negligence after a collision involving a high-speed train killed at least nine people and injured 84 – an incident that will add to fears that the country’s infrastructure is deteriorating.

The commuter train heading to the city of Konya ploughed into a service engine carrying out a track inspection and then crashed into a pedestrian overpass at a station in Ankara at about 6.30am local time on Thursday.

Turkish television showed emergency workers at the scene in snowy conditions trying to free people from carriages trapped beneath the wreckage of the overpass at Marşandiz train station, about five miles from Ankara’s main station.

Three engine drivers are believed to be among the dead and at least three of the 206 passengers onboard remain in a serious condition in hospital.

One passenger, Ayşe Özyurt, told the IHA news agency that the crash occurred 12 minutes after the train had left the main station in Ankara, and that it had not yet gained its maximum speed. “The train was not fast at that time yet,” she said. “Suddenly there was a frightening breakage … and the train was off the rail.”

The cause of the crash is not known, but engineering and rail workers’ unions have repeatedly said cost-cutting programmes and the axing of route inspector jobs five years ago have created safety issues.

There have been eight serious train accidents in the country since the ruling AK party took office in 2002, including a derailment near the city of Çorlu this year that killed 24 people.

Yunus Yener, the chair of the Union of Chambers of Turkish Engineers and Architects, said in a tweet that signalling issues had been flagged on the Konya-Ankara line for some time.

The Ankara governor, Vasip Şahin, said a technical inspection had begun, while NTV television, quoting unnamed officials, said three prosecutors had been assigned to investigate. “Our hope is that there are no other victims,” Şahin said.

Facebook Twitter Pinterest Wreckage covered rail tracks after a collision between a high-speed train and a service train. Photograph: Anadolu Agency/Getty Images

A statement from President Recep Tayyip Erdoğan’s office said those responsible would be brought to justice. The three arrested state railway employees have not yet been named.

Critics of Erdoğan say his presidency has been characterised by a steep decline in public services and associated worries about the erosion of health and safety practices.

In July, 24 people were killed and more than 70 injured when most of a passenger train derailed in Çorlu, in north-west Turkey, after torrential rains caused part of the rail tracks to collapse. Last month 15 people were injured when a passenger train collided with a freight train in the central province of Sivas.

An investigation into the Çorlu incident was later quashed by Turkey’s ruling AK party officials.

Fadi Hakura, an associate fellow at London’s Chatham House, said: “The Turkish government is a big fan of mega-projects, gleaming new buildings, infrastructure expansion, because those things signify progress. There is not the same focus on quality of service or proper management or maintenance.

“Healthy and safety has basically gone out of the window and more construction workers are dying, not because the statutes are not on the books but because the rules are not being enforced.”

Of particular concern to unions and labour organisations is Istanbul’s new airport, where the Turkish labour ministry said this year that at least 27 of the 30,000-strong construction force had died since 2015. Local unions have complained that strikes have been met with force from the authorities, and employees are now working under police supervision.

The government says the new airport, due to open on 31 December – an already delayed date – will be one of the largest in the world.