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ANSA via Associated Press, Milena di Mauro
An excavator is used during recovery operations a day after two commuter trains slammed into one another just before noon Tuesday in Puglia, between the towns of Corato and Andria, Italy, Wednesday, July 13 2016. Delayed rail improvements and the antiquated telephone alert system will be considered as part of the investigation into the violent head-on train crash in southern Italy that killed nearly two dozen people, officials said Wednesday.

BARI, Italy — Italian officials on Wednesday pointed to delayed, EU-financed rail improvements and the "risky," antiquated telephone alert system used in parts of Italy as possible underlying causes of a violent head-on train crash that killed some two dozen people.

Recovery operations continued Wednesday using a giant crane and an extra locomotive to remove the mangled cars and debris of the two commuter trains that slammed into one another just before noon Tuesday in the neat olive groves of southern Puglia.

The official death toll stood at 23, including a farmer working his fields who was killed by flying debris from the crash. The prefect of Barletta, Clara Minerva, said relatives reported another four people unaccounted-for and suggested that their remains could have been scattered within the wreckage, particularly in the area of highest impact.

"Some remains have been recovered, and on these DNA and other tests are underway," Minerva said.

As a result Transport Minister Graziano Delrio put the provisional death toll at 27. Local officials said that of the 51 people originally hospitalized, 27 have been released. Seven of those still hospitalized are in critical condition.

Delrio confirmed that the particular stretch of track between the towns of Andria and Corato didn't have an automatic alert system that would engage if two trains were close by and on the same track. Rather, the system relied on stationmasters phoning one another to advise of a departing train.

The phone system "leaves an entirely human management and is among the least evolved and most risky ways of regulating railway circulation," Delrio told parliament. Under the system, he said, the stationmaster can only allow the train to leave if it is confirmed that the line is free at the arrival station, allowing only one train at a time on the single railway.

He said the single rail track used in the area isn't dangerous if "advanced technology is applied."

Andria Mayor Nicola Giorgino said the crash was particularly tragic and "paradoxical" since work was to begin within a few months to build a second track on the route.

In fact, the work was supposed to have begun years ago, and EU funding was secured when it was first proposed for the 2007-2013 period. According to the national investment and development agency Invitalia, the EU Regional Development Fund had approved 62 percent of the 180-million-euro investment into the north-Bari rail improvement that included a second track for the Corato-Andria line.

But it was never built. Delrio didn't explain why, but noted that Puglia officials had secured funding for the 2014-2020 budget and that bidding for contracts was to have begun July 19.

Trani Prosecutor Francesco Giannella said the delay in the track-doubling work would be part of the investigation. "We will investigate on the delays of the work on the line and on the deficiencies in the security system," the ANSA news agency quoted Giannella as saying.

Wednesday also brought the gruesome task of families identifying the dead. Many relatives wailed outside the Bari morgue, demanding justice, questioning how a single rail could still be in use in 2016 and warning national authorities not to abandon them. Their lament was evidence of the strong distrust many southerners have toward a government that has historically ignored the south in favor of the more-developed north.

"We went around all the hospitals, all day," said Giuseppe Colaleone, the brother-in-law of a passenger. "In the end we came here. My brother said she (his missing wife) had a necklace with the letter M on it, and a scar here, signs that could identify her. A nurse said they have probably identified her."

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.

Delrio stressed that the national government bore no responsibility for the incident, and that security for regional trains was up to the operator in charge, Ferrotramviaria.

Winfield reported from Rome; Colleen Barry contributed from Milan.