The first Tunnel Boring Machine (TBM) began its first drive from Janakpuri West to Dabri and its distance will be 1.2 km.
It will finish the drive in approximately five months and emerge at Dabri in May next year, a DMRC official said.
A total of four TBMs will be used for the tunnelling of approximately 4.2 kilometres from Janakpuri West to Palam.
Another TBM had started tunnelling work between the 5.5 km long underground Hazrat Nizamuddin - Lajpat Nagar stretch on the Mukundpur (Majlis Park) - Shiv Vihar corridor on December 16.
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Presently a total of nine TBMs are operational in Phase III.
DMRC is slated to construct 53-km of underground Metro lines as part of its Phase III construction work for which about 34 TBMs are expected to be used.
A total of 74 tunnels will be constructed in this phase. The tunnelling work between Central Secretariat and ITO on the 9.37 km long Central Secretariat - Kashmere Gate corridor has been already completed.