Mashrak–Thawe Extension Railway was owned by the Government of India and worked by Bengal and North Western Railway.
The 39-mile-long (63 km) metre gauge line from Mashrak to Thawe was opened 12 January 1931.
The Mashrak–Thawe Extension Railway was merged into the Oudh and Tirhut Railway on 1 January 1943.
The railway line was converted to 1,676 mm (5 ft 6 in) broad gauge in 2017.