NEW YORK - Metro-North officials say the two-hour disruption in service Thursday night was caused by human error during an electrical repair project. 

They say the computers that run the railroad's signal system lost reliable power when one of two main power supply units was taken out of service for replacement. 

Officials say that is when more than 50 trains on three lines were forced to stop. 

They say the project should have been analyzed for risks and it should have been performed in the middle of the night or on a weekend, not when thousands of customers are trying to get home. 

It came one day after a stuck train stranded nearly 200 people for about two hours in Westport.

Officials say Metro-North customers deserve better and they sincerely apologize for the inconvenience customers experienced.