The Darjeeling station was renovated in 1891 and Kurseong got a new station building and storage shed in 1896, but the railway was impacted by an 1897 earthquake and a major cyclone in 1899. In 1910, the DHR carried 174,000 passengers and 47,000 tons of goods. The first bogie carriages entered service, replacing basic four-wheel carriages. DHR extension lines were built to Kishanganj in 1914 and Gielkhola in 1915. At Tindharia, the railway works were relocated from behind the locomotive shed to a larger site. The Batasia Loop was constructed in 1919, creating easier gradients on the ascent from Darjeeling. The DHR began facing competition from buses operating on the Hill Cart Road which took less time than the railway to reach Darjeeling. In 1934, a major earthquake in Bihar shook all of Northeast India. Many buildings in Darjeeling were heavily damaged and the railway was also affected, although it soon recovered and played a vital role in transporting repair materials. During World War II, the DHR transported military personnel and supplies to the camps around Ghum and Darjeeling. In 1951, the railway was purchased by the Indian government and was absorbed into the government railway organisation before it was managed by the Assam Railway. Assam Railway (including the DHR) became part of the North Eastern Railway zone in 1952, and part of Indian Railways' Northeast Frontier Railway zone six years later. In 1962, the railway was realigned at Siliguri and extended by nearly 4 miles (6 km) to New Jalpaiguri (NJP) to meet the new broad-gauge line there. The extension began freight service that year, and passenger service in 1964. The locomotive shed and carriage depot at Siliguri Junction were moved to NJP. The railway was closed for 18 months during the Gorkhaland hostilities in 1988 and 1989. It was declared a World Heritage Site by UNESCO in 1999. The DHR and its assets, including the stations, line and vehicles, is owned by the government of India and entrusted to the Ministry of Railways. The Northeast Frontier Railway documented the railway in a comprehensive register, and handles its day-to-day maintenance and management. Several programs, divisions and departments of Indian Railways are responsible for operating, maintaining and repairing the DHR. It is protected by the 1989 Railway Act and the stipulations governing public property. All the steam locomotives currently in use on the railway are B-Class, built by Sharp, Stewart and Company and later the North British Locomotive Company between 1889 and 1925.