Copper thieves delayed 40 Metro-North trains Friday morning by ripping up hundreds of feet of cables from the tracks in The Bronx the night before, authorities said.

About 350 feet of cable were taken in the heist from the tracks just north of the Williams Bridge station — triggering a thunderous noise and flashes of light from the raw electricity the cable had used to power trains. No one was hurt.

There was only track available for the Harlem and New Haven lines between 11:30 p.m. and 6 a.m., and just two by 6:45 a.m.

Trains were delayed by congestion caused by the limited track space. The final track was repaired by 1:30 p.m.