ROME, July 13 (UPI) -- Italian authorities said they are focusing on an alert system that relies on telephone calls following the head-on collision of two trains that killed at least 27 people.
Human error remains the main line of inquiry, railway police Com. Giancarlo Conticchio said. Officials are analyzing one of the train event recorder from the scene of the crash on the remote single-track line north of the city of Bari in Italy's southern Apulia, or Puglia, region.
"Surely one of the two trains shouldn't have been there," Conticchio said. "And surely there was an error. We need to determine the cause of the error."
The section of the railway track in which the crash occurred did not have an automatic alert or brake system.
Meanwhile, rescue workers were still searching the wreckage for passengers. There was no official manifest on either train, both of which pulled four carriages so officials said they are having a difficult time determining how many people were on board.
At least 15 people were hospitalized, some in critical condition. Most passengers had no warning of the coming crash.
"I was thrown forward, I don't know what happened, it all happened so quickly. I saw my mother on the ground, my father and my sister bleeding. The people on the train helped us," a woman who was eight months pregnant told BBC News.
The collision happened around 11:30 a.m. local time Tuesday. Italian Prime Minister Matteo Renzi visited the site of the crash and ordered an official investigation.