Jakarta. Jakarta's public ransportation company MRT Jakarta has completed the underground tunnel connection for the capital's Phase 2A north-south metro extension after a tunnel boring machine (TBM) successfully broke through at Mangga Besar Station, marking a key milestone in the project's construction.

The breakthrough by TBM 1 at the southern side of Mangga Besar Station connects approximately 5.8 kilometers (3.6 miles) of underground railway, completing the excavation of the Phase 2A tunnel alignment.

"The Phase 2A tunnels are being constructed using three tunnel boring machines across three contract packages: CP201 (Bundaran HI–Harmoni), CP202 (Harmoni–Mangga Besar), and CP203 (Mangga Besar–Kota)," MRT Jakarta Construction Director Weni Maulina said in a statement on Thursday.

The tunnel at Mangga Besar Station reaches a depth of 28 meters (92 feet) below ground, making it one of Indonesia's deepest metro tunnels, comparable to the underground section at Sawah Besar Station.

According to Weni, TBM 1 under the CP202 contract excavated a 395-meter tunnel between Harmoni and Sawah Besar stations, as well as an 800-meter connecting tunnel between Sawah Besar and Mangga Besar. During construction, the machine passed beneath a canal located between Gajah Mada and Hayam Wuruk streets.

Construction is continuing on the remaining southbound tunnel connecting Kota Station to Bundaran HI. MRT Jakarta aims to complete all tunneling work for Phase 2A in the fourth quarter of 2026.

As of June 25, overall construction progress for MRT Jakarta Phase 2A had reached 61.8%.

The first section of the extension, linking Bundaran HI and Monas, is scheduled to begin operations by the end of 2027. The second section, from Monas to Kota, is targeted for completion and operation by the end of 2029.

The Phase 2A extension will expand Jakarta's existing north-south MRT line deeper into the city's historic center, improving connectivity and supporting efforts to reduce traffic congestion in Southeast Asia's largest metropolitan area.