During First World War, a line was laid from Khanai (near Bostan and 30km north of Quetta) to Hindubagh (now Muslimbagh). The area around Hindubagh had Chrome mines, which was used in munitions of First World War. The railway line at that time was a private siding for the ‘Balochistan Chrome Ore Company’.
The work started on Khanai-Hindubagh line in 1916 and was opened for rail traffic in 1921. In 1927, the Hindubagh to Qila Saifullah section was opened and finally the section up to Zhob was opened in 1929.
It became part of NWR's Northern Frontier narrow gauge, Zhob Valley Railway network.
Chromate was discovered in the Zhob area in 1901. It was mined by the ‘Baluchistan Chrome Co’ . They had been asking for a railway to be built for the transport of the chromate ore since the formation of the company in 1902. In 1910, the records show that the Company was treating to abandon their mining concession unless a railway be built due to the costs of conveying the ore by camel. In response to the requirements of the arms industry for chrome in World War One, building of the line eventually started in 1916. It opened as a private siding in September 1917 from Khani, just north of Bostan on the broad gauge(BG) North Western Railway(NWR) .
The 2ft 6in/762mm narrow gauge(NG) line ran from Khanai in a north-westerly direction with stations at Gwai (Mile 5 miles from Khani); Zaghan(Mile 12); Tor Aghbargi (Mile 22); Kanr Mehtarzai(Mile 30); Rahmgul(Mile 36); Hindubagh(Mile 46) and Khatoka Junction , formerly known as Gitzai Junction(Mile 52). The chromate mines with rail loading facilities were located beyond Khatoka Junction. They were Mine 26(1.43 miles from Khatoka Junction); Mine 27(3.93 miles); Mine 70(5.68 miles); Mine 34(5.93 miles) and Mine 136(8.68 miles) . There was a separate branch to Mine 135(2.18 miles from Khatoka Junction). The ore was transported by hopper wagons and transferred to BG wagons at Khani by ore drops built over the BG track on trestles 
- “Industrial Railways and Locomotives of India and South Asia” compiled by Simon Darvill. Published by ‘The Industrial Railway Society’ 2013. ISBN 978 1 901556 82-7. Available at http://irsshop.co.uk/India. Reference: Entry IA06 page ....