Four children, including two from the same family, have died after a train struck an electric transport wagon in which they were travelling near the eastern Dutch town of Oss, local media have reported.

A fifth child, also from the same family, and the woman driving the wagon, known as a bolderkar or Stint, were critically injured. The ANP news agency said the accident happened at about 8.25am on Thursday on a manned level crossing as the woman was taking the children, aged between four and 11, from the before-school daycare centre where she worked to local primary schools.

Witnesses told the Algemeen Dagblad newspaper that the barriers on the level crossing had been lowered but that the vehicle – a mode of transport popular with daycare centres in the Netherlands and Belgium for ferrying young children around – passed underneath them and became stranded on the tracks.

Some witnesses said the the driver appeared to have lost control and was calling for help as the train approached.

Police said there had been a “very serious accident”. The mayor of Oss, Wobine Buijs-Glaudemans, said it was “a black day for the town. Every family will be affected by this.”

Roger van Boxtel, the chief executive of Dutch Railways, tweeted: “How terrible, this dramatic accident in Oss. Our thoughts are with the victims, their relatives and friends, the wounded and with the travellers and our colleagues who were there. What grief.”

An example of a bolderkar or Stint, the type of vehicle involved in the Oss collision. Photograph: Joop Hermans/Stint

Although approved for road use by the transport ministry, the vehicles are regarded by the Dutch road safety organisation VVN as dangerous. A VVN spokesperson, José de Jong, told the Algemeen Dagblad it was vital that drivers had proper training. “We are aware of other accidents,” she said.

Edwin Renzen, who invented the vehicle – described as cross between a cargo bike and a Segway – in 2011, told the state broadcaster NOS that the accident was “every parent’s worst nightmare. This is a terrible blow. Awful.”

Two trauma helicopters and multiple ambulances took the victims to hospital, where the two survivors were in intensive care, the Brabants Dagblad reported. Local authorities were offering emergency information and psychological support in a neighbourhood centre.

All train traffic on the line was suspended while a team from the national accident investigation unit examined the scene. A police helicopter took aerial photographs of the scene to try to understand how the collision could have happened at a manned crossing with a designated cycle lane.

An average of 11 people are killed on Dutch level crossings each year, a figure described as “unacceptable” by the national safety board OVV in a report in July. The board criticised the infrastructure ministry’s lack of focus on the problem.

The report said the Netherlands had more roads crossing railways than any other EU member nation. “This is not a good combination,” it said.