SINGAPORE - A rail crack delayed southbound MRT services between Woodlands and Ang Mo Kio from 6.25am on Thursday.
It was the third instance of a rail crack delaying train services in Singapore since late last month.
An SMRT spokesman said the crack was detected between Yio Chu Kang and Ang Mo Kio stations.
The delay was as much as 40 minutes initially, but this was later brought down to 15 minutes, The Straits Times reported on its website.
SMRT engineers were quickly on site and the rail operator said it was investigating the incident.
It said "G-clamps" had been used, as in the previous cases, to temporarily stabilise the affected area.
It then imposed a speed restriction on trains on the affected stretch of the track.
The speed limit would remain for the entire day and repairs to rectify fault would be done after the trains stopped running for the day, SMRT said.
Rail cracks were rare on the Singapore rail network till last month, occurring, on average, only once a year, The Straits Times said.
Now, in just over a month, it has happened thrice and on different parts of the North-South Line each time.
The two earlier incidents, on April 29 and May 18, were similar in many respects, SMRT had said.
Both occurred at rail joints welded between old and new rails by the same contractor.
After a preliminary analysis, SMRT began probing four main areas to determine why the rail cracks occurred: the material used, workmanship, stress factors and welding process.
"We are conducting a thorough inspection of all suspected rail joints in the entire network and will be taking the appropriate remedial actions," SMRT vice-president for corporate marketing and communications, Ms Kalai Natarajan, had said.
"This is in addition to our regular patrols and tests carried out on all our tracks to detect rail flaws in order to ensure rail integrity." SMRT and the Land Transport Authority are also speeding up work to replace all the sleepers on the North-South and East-West lines by 2016.
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