TEHRAN — A passenger train partially derailed in eastern Iran early Wednesday, killing at least 17 people and injuring 50 more, including some critically, the authorities said.

Initial details about the disaster involving the train, which was reportedly carrying about 350 passengers, remained unclear, but there were fears that the number of casualties could rise.

Four of the seven cars in the train derailed in the early morning darkness near the desert city of Tabas, about 340 miles, or 550 kilometers, southeast of the capital, Tehran, Iranian state television reported.

Rescue teams with ambulances and helicopters arrived at the crash site, in a remote area with poor communications links.

Aerial footage of the desert site of the disaster showed train cars on their side, with some rescuers running at the scene as they tried to care for those injured. Ali Akbar Rahimi, the governor of Tabas, was quoted by Iranian media as saying the number of deaths could rise after rescuers searched the train cars.

State television later aired images from a hospital where the injured were taken for treatment. One of those injured told the broadcaster they felt the train suddenly brake and then slow before the derailment.

“Passengers were bouncing in the car like balls in the air,” said the injured passenger, who was not identified.

The derailment took place about 30 miles outside of Tabas on the rail line that links the city to the central city of Yazd, about 190 miles to the southwest.

Iranian media reported that the crash is under investigation. Initial reports suggested the train collided with an excavator near the track, though it was not immediately clear why an excavator would have been close to the train track at night. One official suggested it could have been part of a repair project.

Iran’s worst train disaster came in 2004, when a runaway train loaded with gasoline, fertilizer, sulfur and cotton crashed near the historic city of Neyshabur, killing close to 300 people, injuring 460 others and damaging five villages. Another train crash in 2016 killed dozens and injuries of scores of people.