Construction continues in July 2017 at the Loudoun Gateway station, part of Phase 2 of the Silver Line rail project. (Katherine Frey/The Washington Post)

More than 1,700 concrete panels installed at five Metro stations being built as part of the second phase of the multibillion-dollar Silver Line rail project have defects, and the company that manufactured them is the target of a criminal probe, officials said Wednesday.

Charles Stark, executive director of the rail project, said his staff, along with lead contractor Capital Rail Constructors, identified problems with the precast panels, manufactured by Universal Concrete Products, that could allow water to seep in, leading to rust and cracking in the stations’ walls.

Stark said the problems will not compromise safety, but they need to be addressed because they could affect the life span of the $5.8 billion project.

“We are confident at this point that the mitigations are solutions that will result in not just a safe system, but one that will last 100 years,” Stark said.

Officials at Universal Concrete did not respond to requests for comment.

Phase 2 construction on Metro's Silver Line at Dulles International Airport continues in July 2017. (Katherine Frey/The Washington Post)

The Federal Transit Administration said it is aware of the “potential issues” related to the project. The FTA, part of the U.S. Department of Transportation, is involved with the project because the Department of Transportation contributed $900 million in funding, in addition to nearly $2 billion in federal loans. The agency referred all other questions to the Department of Justice, which declined to comment.

A spokesman for the Department of Transportation’s Office of the Inspector General, which conducts audits and investigations of DOT programs, said: “We cannot comment on an active, ongoing investigation.” Officials also declined to provide details on what the probe covers or who is leading it.

Metro, which will operate the extension once construction is complete, said it is aware of the criminal investigation but is not a party to it because the project is managed by the Metropolitan Washington Airports Authority (MWAA).

Metro spokeswoman Sherri Ly said the transit agency is working with MWAA to resolve the problems.

“We are aware of the concrete issues and have reached an agreement with MWAA and the contractor on long-term remediation, including future maintenance,” Ly said in a statement. “We continue to work with the parties involved to ensure that Metro does not incur future expenses related to the concrete panels.”

The second phase of the Silver Line, one of the largest rail projects under construction in the United States, will add six stations to the five that opened in 2014 and extend Metro service to Dulles International Airport. The second phase also will connect the fast-growing suburbs of Loudoun County to the Metro system.

Stark said the problems with 1,750 panels were identified last year. News of the problems was first reported by NBC4.

“Working closely with representatives for the Metropolitan Washington Airports Authority and independent testing professionals, [Capital Rail Constructors] determined that these panels do not present a safety risk to workers or the public; however, some of the panels require corrective action,” a spokeswoman for Capital Rail Constructors said in a statement. “The corrective plan includes sealing to improve durability and replacing precast when durability requirements cannot be met through sealing.”

At least 65 panels did not meet project standards and are being replaced.

Stark said the remaining panels will be treated with a special coating designed to insulate them from water. He said the treatment is cost-effective and will provide the level of protection needed to prevent water seepage. However, the sealant will have to be reapplied every 10 years.

The cost for replacement and treatment will be paid by Capital Rail Constructors and Universal Concrete, officials said. They said the work is not expected to further delay the expected 2020 opening of the second phase of the rail line, which is already 13 months behind schedule.

The panels were installed at five stations: Reston Town Center, Herndon, Innovation Center, Loudoun Gateway and Ashburn. The panels were not used at the Dulles Airport station; those panels were manufactured by a different contractor.

In addition, Stark said officials have found cracks in concrete support girders at nearly 110 areas along the 11.4-mile rail extension.

He said the cracks are not the result of a manufacturing problem, but rather with how the girders were installed. The girders were not manufactured by Universal Concrete.

Stark said workers will drill holes in the girders, fill them with cement grout to push out excess water and install waterproof coverings to seal them.

This is the second time that officials have run into problems with concrete structures that are part of the rail project. In 2015, officials halted work at the Dulles Airport station because cracks appeared in the concrete girders that support the tracks. The girders were manufactured by a different contractor, Chesapeake, Va.-based Coastal Precast Systems.