Train services were disrupted across the central and northern Netherlands during Tuesday’s morning rush hour by pipes deliberately attached torails, the infrastructure operator ProRail said.

Around 20 incidences were reported.

The broadcaster NOS showed long, thin pipes being removed from the tracks.

“At this stage, it appears to be a deliberate disruption of train services caused by human action. It is not yet known who is responsible or what the motive is”, ProRail said, adding that national police were investigating.

The pipes not only disrupted rail travel but also road traffic as several level crossings had to remain closed, ProRail said in a statement.

It was unable to say when services might return to normal.