A passenger train collided with a freight train in northern Italy in heavy fog on Friday, killing at least 13 people and injuring dozens, rescue officials said. The head-on crash turned several cars into a wreck of buckled metal.

One train car was ripped apart by the forcaid.

The trains collided at 12:50 p.m. in a rural area of Bolognina di Crevalcore, north of Bologna. The Transport Ministry (search) said it was opening an investigation into the cause of the accident.

According to the ANSA news agency, investigators were studying the possibility that one train failed to stop at a red light and wait for the other train to pass on a second track.

A prosecutor in Bologna heading the investigation declined to comment on the report.

"Tomorrow we will begin to get more details," said Prosecutor Luigi Persico, adding that an expert was heading to the scene.

One passenger said that before impact the train seemed to be traveling at normal speed and he hadn't felt the brakes kick in. Passenger Steve Djaumen from Cameroon said he and others were able to push open a door and climb out.

"From the car in front of ours, which was completely destroyed, we heard people screaming for help," he told ANSA.

The misty weather and rough countryside complicated rescuers' early efforts to reach the site, one rescue official said.

"Unfortunately, as you can see, the terrain offers scarce mobility for ambulances," fire chief Mario Morcone told reporters. "The fog didn't make it easy to get here."

Rescuers lifted several injured passengers out of the train on hard-backed stretchers and loaded them onto ambulances. Bodies in bags were lined up in a flat misty field near the scene of the crash.

Officials planned to work into the night to clear the tracks, cutting pieces from the wreckage of the train under floodlights and lifting them away with a crane.

Several seriously injured people were taken to nearby hospitals, and about 50 people were treated at the scene for minor injuries, ANSA said. Officials originally put the death toll at 14, then lowered it, saying confusion arose because of difficulty of identifying bodies.

The Civil Defense department said around 100 people were on board the passenger train, which was traveling south from Verona to Bologna. The freighter, which carried long metal rods, was headed north from Rome to San Zeno Falzano.

French President Jacques Chirac offered his condolences in a letter to Italian Premier Silvio Berlusconi.

Though most train accidents in Italy are minor, the country has occasionally seen deadly crashes. The most recent was in July 2002, when a train from Palermo to Messina derailed in northeastern Sicily, killing at least eight people.

Europe's most recent deadly train crash was in November in Britain. Seven people were killed when a train struck a car on a level crossing west of London.