AKIPRESS.COM - At least 25 people died and dozens were injured on Tuesday when two passenger trains collided head-on at high speed in southern Italy, sending debris flying into surrounding olive groves, Reuters reports.

Three carriages were torn apart by the violence of the impact after the two trains hit each other while traveling down the same stretch of track linking the small towns of Corato and Andria in the southeastern Puglia region.

Rescue operators raised the death toll to 25 on Tuesday evening after a day of frantic rescue operations, and warned that it could climb higher as some of the 50 injured were in serious condition.

Authorities urged blood donors to go to local hospitals.

There was no immediate indication of what had caused one of Italy's worst train disasters in recent years, but the government promised a full and swift investigation.

"Tears and grief for the victims and their families, but also a lot of anger. We demand clarity over what happened in Puglia this morning," Prime Minister Matteo Renzi said on Twitter, before making his way to the region to meet with rescuers and local politicians.

Lacrime e dolore per le vittime e le loro famiglie. Ma anche tanta rabbia. Pretendiamo chiarezza su ciò che è avvenuto in Puglia stamani.

— Matteo Renzi (@matteorenzi) July 12, 2016

The crash happened at around 11.30 a.m. (0930 GMT) on a fiercely hot summer's day.

Both trains were comprised of four carriages. The front carriages on each were pulverized as they slammed into one another. Sky Italia TV said one of the drivers had died, with no word yet about the fate of the other one.

The last major rail disaster in Italy was in 2009 when a freight train derailed in Viareggio, in the center of the country, and more than 30 people living close to the tracks died in the subsequent fire.