MILAN — A high-speed passenger train derailed in northern Italy before dawn on Thursday on the heavily used Milan-Bologna line, with the motor car completely detaching and slamming into a railroad building, killing two railway workers and injuring 27 people, authorities said.

The state-railway Freccia Rossa train went off the rails while traveling at nearly 300 kph (180 mph), Civil Protection chief Angelo Borrelli told state radio.

State railways said the two fatalities were train engineers.

Authorities said the crash occurred about 5:30 a.m. (0430 GMT) in the countryside outside the town of Lodi.

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

Aboard the first passenger car, for business-class, which overturned, there was only one passenger, officials said.

The rest of the cars remained upright.

Given the early hour, the train was uncrowded, with only about 30 passengers in all aboard, police said.

Rescuers had to help some passengers out of the train.

Fabiano said that work had been done on that stretch of line during the night. But he said it was unclear if that was a factor in the crash, whose cause was under investigation.

Borrelli said the high-speed state railways train had departed from Milan at 5:10 a.m. (0410 GMT) and was headed south to Bologna when it derailed. Borrelli said two of the injured were in serious condition, while the other 25 were less seriously injured.

The passenger train run is part of a popular high-speed rail service known as Freccia Rossa, or the Red Arrow service. Its southern destination was supposed to be Salerno, a port city south of Naples.

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