SINGAPORE - Mobile service along the Circle Line resumed at about 10.30pm on Thursday (Nov 3) after a suspension of more than an hour.

The suspension was to facilitate tests for the source of a signal interference which disrupted train service on Wednesday.

"Telco signals will progressively resume along Circle Line," SMRT said in a tweet.

M1 also announced on on Facebook at 10.32pm that mobile service had resumed on the line. Singtel and Starhub said their services were back up shortly after.

Mobile operators and the Land Transport Authority said at about 8.45pm that mobile service along the Circle Line would be suspended on Thursday night.

"On instructions from the authorities, mobile network equipment along the Circle Line will be suspended until 10.30pm," M1 announced on Facebook.

"During this period, you will not be able to make calls, send messages, or access the Internet."

Starhub said, also on Facebook: "We have been instructed to turn off mobile services in the Circle Line. During this period, you will not be able to make calls, send SMS or access the internet when travelling on Circle Line."

Singtel's update also confirmed that service was to be suspended until 10.30pm.

"Due to ongoing checks on Circle Line signalling system by LTA, mobile customers will not be able to receive mobile signals at all CCL stations from Harbourfront to Bayfront from now to 10.30pm tonight," it said in a Facebook post.

According to the Land Transport Authority (LTA), the mobile signals were affected "when travelling in tunnels".

The suspension comes after a mysterious signal interference resurfaced on Wednesday morning, interrupting train service on the Circle Line for three hours during peak hour.

Service ground to a halt for more than an hour at five stations between Botanic Gardens and Serangoon.

All three telcos warned customers on Wednesday that mobile coverage along the MRT line may be suspended to aid investigations.

The signal interference first occurred in late August, disrupting service on the Circle Line for a week.

This was traced to an unknown signal interference, but it disappeared before the source could be traced by SMRT.