THE HAGUE, Sept. 20 (Xinhua) -- A collision between a train and an electric child cargo bike in Oss, southeast Netherlands, on Thursday killed four children, ranging from 4 to 11 years old.

The accident occurred around 8.30 a.m. local time at a guarded railway crossing, near the Oss West station. Four children died, one got seriously injured and one adult was also seriously injured, the police reported.

The electric cargo bike of a childcare center had already dropped some kids at a primary school and was on its way to the next primary school in Oss. The five children are from three different families, the police stated.

How the accident could happen is not clear yet. The cause of the collision is still under investigation, the police said at a press conference.

Witnesses told national broadcaster NOS that the cargo bike did not stop when it approached the railroad crossing and the driver shouted that it was not possible to brake. Then the vehicle was grabbed by the train.

"Today, every family is hit," said Oss mayor Wobine Buijs at a press conference. "This is a black day, a day that you hope will never come. My thoughts go out to the victims and their relatives."

"I am deeply touched by the incredibly sad news from Oss where four young children were killed in a horrendous accident," said Dutch Prime Minister Mark Rutte. "I wish all those involved a lot of strength with this heavy loss."