Metro officials are pushing for an independent safety agency to inspect the second part of the Silver Line’s construction process, The Washington Post reported Saturday.

Paul Wiedefeld, the Washington Metropolitan Area Transit Authority general manager, asked the Washington Metrorail Safety Commission to conduct a thorough investigation of the project to resolve outstanding safety concerns about the rail line, according to The Post. The Post obtained several documents that outlined setbacks, like construction and performance defects, that WMATA officials have brought to the commission.

“As you know, there are many issues with the project, including several material unresolved performance and construction deficiencies as detailed in the attached three letters that WMATA sent to the Airports Authority in September 2019,” Wiedefeld wrote in a letter, a copy of which The Post obtained, to the commission.

Safety officials told The Post the commission is aware of WMATA’s concerns and will ensure the extension is safe for passengers. The commission is required to conduct an independent safety review of the extension project before the rail line opens, according to The Post.

The Silver Line extension is set to open in the summer, adding six stations to the line running from Ashburn to Dulles International Airport. The project has been delayed several times, most recently tacking on an additional two months in August after construction companies fell behind schedule.

Commission spokesman Zachary Radford told The Post that safety officials have been overseeing the second phase of the Silver Line for more than a year.

“We intend to keep up our efforts to ensure that WMATA commences operations only when all elements are ready for service and all hazards have been properly mitigated,” Radford said.

The Washington Metropolitan Area Airports Authority is overseeing Silver Line construction, but operations will be turned over to WMATA when the extension is finalized, The Post reported.

Leadership from Capital Rail Constructors, the construction company building the extension, said the project currently meets necessary safety standards, according to The Post.