SINGAPORE - Two unrelated faults on the North-South Line on Thursday (June 1) and Friday (June 2) evening were uncovered during system-level performance checks for the new signalling system for the line, the Land Transport Authority (LTA) and SMRT said in a joint statement on Friday (June 2) night.

As testing continues and intensifies, there may potentially be more delays, until the new signalling system - supplied by Thales - stabilises.

The first incident at 6.20pm on Thursday was due to a glitch in the computer server used to manage train schedules. This caused all trains on North-South Line to halt. Although the back-up server kicked in quickly, operations controllers needed 30 minutes to manually reassign train schedules, said LTA and SMRT.

Friday's delays were caused by a fault in signalling equipment known as the Movement Authority Unit (MAU), registered at around 4.48pm.

The MAU fault resulted in slower train movement between Kranji and Admiralty stations. Service recovery took some time as engineers needed to troubleshoot and replace components in the faulty MAU, LTA and SMRT said.

Tests on the new signalling system have been carried out progressively by LTA, SMRT and Thales since March 28.

Phase One began with the last hour of passenger service on selected days.

Phase Two, which began on April 16, involved trials on full-Sunday service. No major incident occurred for the past seven weeks, LTA and SMRT said.

"This gave us the confidence to move into Phase Three this week (May 29) which involves full-day weekday trials."

This was when the two unrelated faults were revealed, during system-level performance checks.

The transport authority and train operator said in their statement that signalling trials are part and parcel of new signalling systems and are carried out to help train operators identify and resolve teething problems.

LTA, SMRT and Thales engineers are intensifying system-level checks.

"We are very sorry for the inconvenience caused and we seek the patience of commuters."