BOSTON (AP) — Half of the maintenance work scheduled to take place during a monthlong shutdown of one of the Boston public transit system’s subway lines has been completed, officials said Friday.

The Massachusetts Bay Transportation Authority suspended passenger service along the 11-mile (17.7-kilometer) Orange Line on Aug. 19 to complete five years’ worth of track and signal replacement and maintenance as well as other projects in 30 days. Service is scheduled to resume at 5 a.m. on Sept. 19.

Agency General Manager Steve Poftak said at a news conference that he’s “cautiously confident” the work will be completed on time.

“Right now the Orange Line is fully mobilized with multiple crews in multiple locations doing a tremendous amount of work, work that requires a great deal of choreography and staging, and just an amazing amount of cross departmental cooperation here at the T,” he said.

As an example of the work getting done, he said crews had replaced 900 feet (274 meters) of track in two days. Under normal overnight repair schedules, only 39 feet (12 meters) of track can be replaced per day.

The work is part of the MBTA’s response to a safety Federal Transit Administration review following several problems and accidents that have led to injuries, and in one case, the death of a rider. The FTA released a scathing 90-page report earlier this week that said the MBTA has for years prioritized capital projects over safety and maintenance.

Even while the FTA’s review was ongoing, a fire on an Orange Line train in July sent passengers scrambling out of windows and prompted one to jump into a river.

During the shutdown, the transit agency is providing shuttle buses between stations, while commuter rail lines are running with increased frequency.

The Orange Line normally handles about 100,000 trips per day, according to the MBTA, bringing commuters to work, students to school, and visitors to many of Boston’s top tourist attractions.

When the line reopens, the MBTA will also put 56 new cars into service, Poftak said.