“The investigation is only just beginning, evidence is being collected. Eight of our top investigators are there, on the spot,” said Evgeni Dikov, deputy prosecutor general and director of the National Investigative service for the Bulgarian National Radio. “The speedometer device has been found and the data is yet to be deciphered to see the speed of the locomotive. One of the principal hypotheses we are working on is human error and breaking of the speed limit.We are not ruling anything out.”

Evgeni Dikov said there are many things yet to be clarified – for example whether there is any restriction to the number of tanks in transporting dangerous freight and whether it is admissible to transport propane butane and propylene together. There is uncertainty as regards the so-called buffer carriages as well.

“There is unconfirmed evidence that the train broke the speed limit in the incident zone,” said on his part Veselin Vasilev, CEO of the Railway Administration Executive Agency. “There is no problem with the loading of the tanks, nor is there any preliminary data that the state of the rolling stock was in any way degraded.”

“The railway installations were in good repair and there are no doubts as to the state of the railway track,” he added and laid emphasis on the human factor which is crucial in such events.

“A partial peripheral inspection has been conducted of the derailed tanks, so as not to hinder the fire fighters who were cooling them with water,” said on his part Boicho Skorbanski, head of the Transport Ministry’s accident investigation department. “The situation was grave, with a real danger of more explosions. The technical investigation will begin once the area has been cleared up, so the commission can start their work. The rolling stock and the railway infrastructure will be surveyed.”

Boicho Skorbanski added there has not been such an accident in the country since 1989.