SINGAPORE - Engineers have yet to identify the root cause of Tuesday's train disruption , despite carrying out a comprehensive second round of checks.

In a statement on Thursday, the Land Transport Authority (LTA) also said an independent consultant, who specialises in transit power systems, will be engaged to look into the "overall conditional assessment of the entire power supply infrastructure and other railway trackside installations" from as early as this month.

Meanwhile, LTA and operator SMRT will continue checking the system.

During the second round of checks on Wednesday night, LTA and SMRT engineers conducted visual checks on all trains. Insulation testing between the cables and third rail was also carried out, to ensure that the test components of the power supply equipment are in good working order.

Data loggers monitoring the running rail voltage were also installed at specific points on the North-South and East-West lines ,which experienced power trips.

Train services on the two lines were disrupted on an unprecedented scale on Tuesday for more than two hours from around 7pm, causing commuters to be stranded during the evening peak hour.

An estimated 250,000 commuters were affected that night as two of Singapore's oldest and most heavily-used lines were crippled.

Train services resumed later on Tuesday night, and continued to operate on schedule at normal speeds on Wednesday and Thursday.

The LTA has advised commuters to check for travel updates before starting their trip. Information will be available on the SMRT website, LTA and SMRT Facebook and Twitter accounts, LTA Traffic News and MyTransport.SG.

In case of a service disruption, commuters can continue their journey on the free bus services or use unaffected rail lines.

goyshiyi@sph.com.sg