Train services on the Circle Line were disrupted twice on the evening of Jun. 23, due to a signalling system fault.

At 8:40pm, a signalling system fault occurred between Marina Bay/Dhoby Ghaut and Paya Lebar stations.

The cause was a signalling card failure.

"The fault was traced to a faulty Automatic Train Control (ATC) Channel card. After replacement of the particular card, the system was able to start up successfully, and train services progressively resumed," said SMRT, the operator for the Circle Line.

Services resumed at 9:10pm.

However, the fault re-occurred at 10pm.

This time, even though the operator used three sets of cards to recover the Automatic Train Control, the fault persisted.

Bus bridging services were activated for Circle Line commuters.

Here are photos of the scene outside train stations sent by Mothership readers:

SMRT's engineers alongside their counterparts from LTA and Alstom (the rail system supplier) worked through the night to rectify the issue.

SMRT said that they were able to isolate the faulty cards and recover the Automatic Train Control before the start of passenger service on Jun. 24.

The operator also apologised for the service disruption.

In a subsequent update on Jun. 25, SMRT said that it has requested Alstom to fly in its signalling specialist to assist with the investigation and "strengthen the local OEM system support".Top images: Mothership reader, SMRT