Rail travel across large parts of the Netherlands ground to a halt on Tuesday after authorities discovered tubes tied to tracks at roughly 20 locations, in what officials are treating as coordinated sabotage.
Rail infrastructure operator ProRail said deliberately placed objects had triggered widespread track-circuit failures.
"Materials were found at multiple locations on the track that were deliberately placed there," said ProRail in a statement.
"This causes section malfunctions. Sabotage appears to be involved," added the operator.
The devices caused signalling systems to read affected sections as occupied, halting all trains through them regardless of whether one was actually present.
The disruption began around 5:30am (CET) and hit the Amersfoort–Zwolle, Utrecht–Arnhem, Arnhem–Zutphen and Zwolle–Leeuwarden routes hardest, with national operator NS reporting severe knock-on delays around Zwolle, Deventer and Amersfoort during the morning commuter hours.
One train struck a tube near Steenwijk, in Overijssel and ProRail confirmed no one was injured.
Timing of disruption linked to Budget Day
Malfunctioning level crossings also disrupted road traffic in affected areas.
The disruption occurred on the same day as Prinsjesdag, the Netherlands' annual Budget Day, when the King traditionally processes through The Hague before large crowds.
Authorities have not said whether the two are connected.
State Secretary for Infrastructure and Water Management Annet Bertram said she was "deeply concerned" and called for a thorough investigation.
The National Police are leading that inquiry. No group has claimed responsibility, and ProRail says it does not yet know who was behind the attack or why.
