SINGAPORE - The Land Transport Authority is looking to installing an electromagnetic shield on MRT trains after a mysterious signal interference disrupted service on the Circle Line three weeks ago.

In a joint statement with operator SMRT Corp on Wednesday (Sept 21), the LTA said it may also change the signal system frequency of the network. The authority said it was also looking at modifying the system "to provide redundancy in the event of signal interference".

The LTA noted that the signalling systems on newer lines such as the Downtown Line and current lines undergoing upgrading such as the North-south and East-west Lines "are already equipped with new features that provide redundancy in the event of signal interference".

The five-year-old Circle Line, however, does not have these features.

In the interim, spectrum analysers - which can detect various transmissions - will be installed in the Circle Line tunnels.

"This measure will be extended to the North East Line, which has the same signalling system," the joint statement read.

The Circle Line was hit by a signal interference between Aug 29 and Sept 2. The undetermined source interferred with communication between trains and the track, causing trains to apply emergency braking intermittently.

This led to longer and jerkier journeys for a week. The problem stopped as suddenly as it started.