Although the switching system was detected since 6 am but by 9 am it was not yet totally resolved.
BTS said the problem will be fixed after midnight while service throughout the day and before midnight will not be disrupted but commuters have to wait longer up to 6 minutes at each station.
The incident stranded several thousands of commuters rushing to work in the morning rush hours to wait in long queues and at some commuters spilling out to the streets, causing traffic jams on many streets, particularly Sukhumvit.
BTS president Anat Arbhabirama said at 9.45 am today that the track switching fault was detected by technicians at 2 am at the stations from Chidlom to Siam.
They then sought permission to replace the switching system which would take the whole day and power supply have to be cut.
But due to the the fact that the power cut would disrupt the whole sky train service which would cause inconvenience to commuters, technicians were then told to replace the switching system at night instead, while train service would continue in the morning as usual but with low train departure frequencies.
He said normally commuters will wait for 2.40 minutes at each station, but due to the track switching fault, waiting time at each station will be 6 minutes.
He admitted that longer waiting time would inevitably cause commuter congestions at stations, particularly at Siam station where commuters will normally exit to change routes.
He said the repair will start at midnight tonight and advised commuters to use subway trains during the period for their convenience, particularly after office hours this evening which will expect congestion problems again at sky train stations.
The fault forced BTS to adjust the Sukhumvit line to avoid the faults.
The temporary routes using today will see the service in Sukhumvit line separated into two sections; Mo Chit-Siam-Mo Chit and Siam-Bearing-Siam.
Due to technical problems between Chit Lom and Siam Stations, passengers has changed train at Siam, and service is normal on Silom Line.
— BTS SkyTrain (@BTS_SkyTrain) February 23, 2016