Superstorm Sandy caused more damage than thought to Amtrak's tunnels in New York region

Amtrak says flooding from Superstorm Sandy caused more damage than first thought to the tunnels that carry trains under New York's Hudson River.

Repairs on damaged tunnels used by trains linking New York with the rest of the Northeast Corridor could cause a service nightmare for hundreds of thousands of people.

Saltwater has caused cracks to concrete walls and corroded tracks and electrical systems. Weekend crews have been working on tunnels under the Hudson River and the East River.

Railroad officials said Thursday longer closures would cut service on Amtrak from 24 trains an hour to six. Amtrak spokesman Craig Schulz says that would create a ripple effect from Boston to Washington.

Amtrak wants to build two additional tunnels. Its engineering report doesn't estimate how long the current tunnels will last.