Italian authorities are trying to determine why two passenger trains collided head-on in southern Italy Tuesday morning, killing 23 people and wounding dozens of others.

News sources are reporting that the crash occurred between between Ruvo di Puglia and Corato, when the two four-carriage trains smashed into each other on a single-track line as they passed through an olive grove. Efforts to free the survivors were complicated by the remoteness of the accident site, which was described in reports as being in the middle of the countryside.

The 40 injured include 10 in serious condition.

Officials fear that the teach toll could climb higher and are urging area residents to donate blood at local hospitals.