A train derailed in Pakistan’s southern Sindh province, killing at least 15 people and injuring dozens more, according to officials.

Several people had already been seen breaking glass to assist passengers in climbing out of the wreckage when rescue teams were dispatched to the scene.

The train, the Hazara Express, was on its way from Pakistan’s largest city Karachi to the city of Rawalpindi when the derailment happened.

Some 10 railway cars were derailed near the Sahara railway station in the city of Nawabshah, roughly 275 km (171 miles) from Karachi.

The country’s Railways Minister Khawaja Saad Rafiq said the train had apparently not been traveling at a fast pace and that an inquiry had been ordered into the cause of the accident. Apparently, the speed of the train at the time of the accident was about 45 kilometers per hour (about 28 mph).

“There can be two reasons: first that it was a mechanical fault, or the fault was created,” Rafiq said. “It might be a sabotage. We will investigate it.”

Local media said dozens of passengers were still trapped in the carriages immediately after the accident. Footage showed people smashing windows to help others escape the wrecked carriages.

The Hazara Express is a daily passenger train from Karachi in the south across most of the legth of Pakistan to Havelian in Khyber Pakhtunkhwa province. It takes about 33 hours to cover the journey, some 1,600 kilometers northward.

Train crashes are common on Pakistan’s poorly-maintained railways tracks, which have antiquated signalling systems and colonial era communications.

Pakistan’s successive governments have spent years trying to secure funds to upgrade the rail network as part of China’s Belt and Road Initiative for infrastructure projects.