The more than four-kilometre extension includes two tunnels and three stations – Lazurowa, Chrzanów and Karolin – as well as a maintenance depot in Mory.
Technical inspections are now under way and are expected to be completed within 60 days.
The fire service has already carried out its checks, while the regional building inspectorate is due to review the new section before issuing an occupancy permit.
Warsaw Mayor Rafał Trzaskowski said the first passengers could use the new stations at the beginning of 2027, provided the inspections are completed on schedule.
Deputy Mayor Tomasz Mencina pointed out that once the extension is operational, the city's metro network will have 42 stations and 44km of track.
Warsaw is also preparing to extend the second line towards the Ursus district.
Meanwhile, work is continuing on plans for the city's third metro line.
Metro Warszawskie president Jerzy Lejk said two bids had been received for the project, both below the allocated budget.
"Financially, we are in a good position," he told reporters, adding that a contract for the design work had been signed in October 2024, with a 36-month completion deadline.
Construction of Warsaw's metro began in the early 1980s.
The first section opened to passengers in 1995, connecting Kabaty with Politechnika station.
(ał)
Source: IAR, PAP