The disrupted Electric Train Services (ETS) on the north-south line is back to full operations following the opening of a single railway track since 3pm today.

In confirming this, Keretapi Tanah Melayu Berhad (KTMB) corporate communications manager Siti Badariah Wan Hanafi said the first train to use the track was an ETS train from Butterworth to KL Sentral at 4.15pm.

"However, passengers should expect a delay of 30 minutes since we are using a single track," she told Astro AWANI.

With the use of this railway, the temporary bus services for the Kampar-Ipoh-Kampar route has also been discontinued.

"There’s no more bus service. It's a full train service now," she said.

In the 3.15am incident on Friday, two locomotives and 40 wagons travelling from Kuang, Selangor to Tasek, Perak, to collect cement, derailed at KM200.3 between Kota Bharu and Lahat.

The two locomotives and 25 empty wagons had blocked two tracks.

The derailment is said to be the worst incident in the 130-year history of the country's rail services.