MILAN -- A high-speed passenger train derailed in northern Italy before dawn Thursday on the heavily used Milan-Bologna line, with the engine completely detaching and hurtling 100 yards before slamming into a train service car on an adjacent track. Two train workers were killed and 28 people were injured, authorities said.

The state-railway Freccia Rossa train went off the rails in the Italian countryside about 5:30 a.m. (0430 GMT) while travelling at nearly 300 kph (180 mph), Civil Protection chief Angelo Borrelli told state radio.

Girolamo Fabiano, a railroad police official, said work had been done on that stretch of track during the night. But he said it was unclear if that was a factor in the crash, whose cause was under investigation by prosecutors and railroad experts.

State railways said the two fatalities were train engineers. Prefect Marcello Cardona said another railroad worker, part of the cleaning staff, was seriously injured. One passenger was seriously injured and 26 other passengers suffered less serious injuries, authorities said.

“The engine car kept going, 100 metres, at high speed,” Cardona told reporters at the crash site, near the town of Ospedaletto Lodigiano.

Besides striking the isolated work car, the derailed engine skirted an unoccupied railways building in its runaway path, narrowly missing it.

Authorities said the crash occurred about 20 minutes after the train had left Milan heading south toward Bologna.

“The engine car car derailed, detached completely and kept going,” Girolamo Fabiano, a railroad police official told state radio. ”Then the second car derailed.“

Cardona said it was fortunate that, due to the hour, the train wasn't crowded. Police said it had about 30 passengers. Only one passenger was in the first car, a business-class car, that ended up on its side, an a couple of passengers each were in the next few cars. The train passenger cars further back remained upright.

One passenger, an unidentified man interviewed by state TV, likened the moment of the crash to being on a roller-coaster for 20 seconds.

Rescuers had to help some passengers out of the train.

The passenger train run is part of a popular high-speed rail service known as Freccia Rossa, or the Red Arrow service, which links Italy's north and south and is used by business people and tourists as well as locals.

Rail traffic was diverted to local tracks, with delays of about an hour reported.

Italian President Sergio Mattarella in a condolence message lamented the deaths. He urged a swift investigation to determine the derailment's cause “to guarantee the right of citizens to safety on transport.”

In other recent derailments near Milan, three people were killed and more than 100 injured when a regional train derailed on another line in January 2018.