The school group were reportedly crossing the tracks at Leobendorf in Lower Austria to reach a train on the other side to take them back from Vienna after visiting the castle Burg Kreuzenstein, said a police spokesperson.
According to witnesses the level crossing had been lowered for a train that passed without stopping just seconds after the children aged between 10 and 12-years-old had crossed the line.
One of the adults accompanying the children had reportedly climbed under the level crossing to try and reach the train before it departed and the rest of the group followed.
Police in Lower Austria have narrowed down the group to 17 possible schools in Vienna and have released a description of the three adults, all thought to be women.
Witnesses say one of the women had long brown hair and wore an orange t-shirt, the second had long blonde hair and was dressed in white, while the third had a short hair cut. The incident happened on June 28th.
Anyone with relevant information are asked to call police on 059133-3240.
If caught, the women could face charges of endangering the safety of children through negligence.