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

As the investigation progressed, 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 on the sole rail line just before noon Tuesday in the neat olive groves of southern Puglia.

The official death toll stood at 23, including the two train engineers and 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.

Local officials said that of the 51 people originally hospitalized, 27 were released. Seven of those still hospitalized were in critical condition. One of the injured was a 7-year-old boy whose grandmother was killed.

"Today is his 7th birthday. He doesn't know about his grandmother," said Giovanni Gorgoni, head of Puglia's health department, adding that the boy had a slight fever from an infection from the flying shards, but no broken bones.

In a briefing to Parliament, Transport Minister Graziano Delrio confirmed that the particular single 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. Rather, the system relied on stationmasters phoning one another to advise of a departing train and proceed only if the receiving station confirmed the single track was free.