Metro closed the tunnel Dec. 17, reopened it Dec. 18, then closed it again Dec. 19. It has remained closed.

The computer system, installed this year, is designed to let operators control signals, ventilation, elevators, security cameras and lights from a control center near Safeco Field in an emergency.

Workers found suspected flaws in some of the circuit boards.

Sound Transit spokeswoman Linda Robson said Monday that the circuit boards have been replaced, and workers will monitor the tunnel and run simulations.  She said there is a "high level of confidence" the problem has been fixed.  There still has been no word of reopen.  Learn more at http://www.seattletunnel.org/.