The underground section of Corridor II, also known as the North–South or Blue Line, of the Patna Metro Rail project is expected to be completed by the end of 2026, with construction progressing steadily beneath some of the city’s busiest areas.

The 7.9 km underground stretch runs from a ramp near Rajendra Nagar to Patna Junction, which will serve as an interchange station between Corridor I and Corridor II. The section includes six underground stations. Project engineers said most of the tunnelling work has already been completed, with only about 2 km remaining. To accelerate progress, the Delhi Metro Rail Corporation has deployed four tunnel boring machines to construct twin tunnels along the route.

A 5 km tunnel from the Moin-ul-Haq Stadium side towards PMCH has been completed. At the other end, a 1.2 km stretch from Akashvani is nearing completion and is close to reaching Gandhi Maidan station. One tunnel boring machine launched from Moin-ul-Haq Stadium achieved a breakthrough at PMCH on December 10. The remaining works comprise two short sections of around 900 metres each, between PMCH and Gandhi Maidan, and between Moin-ul-Haq Stadium and Rajendra Nagar.

Officials from the Patna Metro Rail Corporation said the underground works are on schedule for completion by 2026. Once finished, the section will integrate with the elevated priority stretch of Corridor II, where partial services began in October 2025. This will enable metro services along the entire 14 km route from Patna Junction to the Patliputra Inter-State Bus Terminal.

Construction of all six underground stations is being carried out simultaneously. Around 40 per cent of the total civil works have been completed, with station designs prioritising safety, passenger comfort and ease of access.