MILAN - Two Italian commuter trains collided head-on Tuesday in the southern region of Puglia, killing at least 22 people and injuring scores more, officials said. At least two passengers were pulled alive from the crumpled wreckage as the rescue operation ground on in the scorching heat.

Survivors described being thrown forward violently and then freeing themselves from a tangle of metal and body parts. Eyewitnesses compared the scene to a plane crash.

"I was thrown forward," said one survivor, who is eight months pregnant. "I saw my mother on the ground, my father and my sister bleeding."

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Railway police Commander Giancarlo Conticchio told Sky TG24 said that the number of dead was 22 with 43 people injured, adding that the final toll could still be higher.

"Surely one of the two trains shouldn't have been there. And surely there was an error. We need to determine the cause of the error," Conticchio said.

Another official stressed the final toll would not be known until the train cars had been pulled apart; a giant crane arrived at the scene to remove the mangled debris.

Rescuers work at the site where two passenger trains collided in the middle of an olive grove in the southern village of Corato, near Bari, Italy, July 12, 2016. REUTERS/Alessandro Garofalo

The two trains, each with four cars, collided head-on in an olive grove on flat terrain between the towns of Andria and Corato on a line with just a single track. The accident occurred around 11:30 a.m. some 30 miles northwest of the Puglia regional capital, Bari.

"It's a disaster as if an airplane fell," Corato Mayor Massimo Mazzilli said on his Facebook page, where he posted photos of the crash.

One elderly couple described their ordeal to local television Telesveva. The man, his head covered in gauze, said he was knocked to the ground, while his wife, still barefoot, described how she came across body parts as she freed him.

"I pulled him from under the debris, myself barefoot, from under the debris and metal," the woman, who was not identified, told local TV. "I went to my husband screaming. I pulled him by the legs and feet. I climbed past people in pieces, how sad. There was nothing I could do.

Another survivor described the scene as "hell."

Premier Matteo Renzi traveled to the scene, where prosecutors and investigators were at work trying to determine why two trains were on a single track.

"We must begin to understand the causes of this tragedy that has saddened the whole country," transport minister Graziano Delrio said at the site, announcing a commission of inquiry. "The crash was certainly violent. Extremely violent."

The cars clearly slammed into one another: They rested crumpled together like an accordion, off the tracks at sharp angles. News reports said rescue workers pulled a small child alive from the rubble.

Riccardo Zingaro, the chief of the local police in Andria, told Sky it was "a great tragedy." Some rescue workers seemed overwhelmed by the scene and the heat.

"The impact was significant, and we are now verifying the consequences," said Giovanni De Siervo of Italy's civil protection service.

A field hospital was set up in the nearby fields to treat the numerous injured, who were also being transported to hospitals.

"Some of the cars are completely crumpled and the rescuers are extracting people from the metal, many of them injured," Zingaro told ANSA at the scene.

Premier Renzi, said the train crash "is a moment of tears" and pledged not to stop investigating until a cause was determined.

The trains were operated by a private, Bari-based rail company, Ferrotramviaria, that connects the city of Bari with Puglia towns to the north and the airport. Ferrotramviaria's website said its fleet comprises 21 electric trains, most with four cars each. The line serves mostly students and commuters.

In a phone interview with state TV, Ferrotramviaria director general Massimo Nitti said the dynamics of what went wrong are still to be determined, but it is clear "one of the trains wasn't supposed to be there" at the same time as the other.