The structural issues that have slowed construction of a massive new transit hub in Silver Spring are more serious than Montgomery County officials suspected, they said Friday.

County Executive Isiah Leggett (D) said earlier this week that the opening of the Silver Spring Transit Center had been pushed back to June and that the county expected the cost of the project to reach $101 million. But officials now say that they don’t know when they will be able to open the facility, which is to bring Metro, MARC, Ride On, taxis and intercity buses to a single site in Silver Spring’s revitalized downtown.

The facility’s structural integrity had already emerged as a concern, and an engineer’s assessment delivered to the county Friday concluded that at least some of the cement was improperly poured and must be redone.

“They’re out of compliance of the WMATA standards,” said ­David E. Dise, the county’s general services director, referring to the Washington Metropolitan Area Transit Authority. “It is not even in compliance with industry standards.”

Dise declined to provide the engineer’s report, saying that it had not been reviewed by ­WMATA, the Maryland Transit Administration or the Federal Transit Administration.

Facchina Construction, a La Plata-based subcontractor that was in charge of pouring the cement, and Foulger-Pratt, the Rockville-based general contractor for the transit center project, did not respond Friday to requests for comment.

A consulting group hired by the project’s engineer, Parsons Brinckerhoff, will assess the hub so county officials can determine how to fix the cement problem. Dise said he did not know how long the study would take.

Initial concerns were related to several locations on the third level, where cement covering the facility’s reinforced steel structure was determined to be too thin and could degrade over time, leaving the steel exposed and threatening the integrity of the building.

Now, Dise said, the county has found that the problems are more serious and that the facility needs “major repairs.”

Dise said earlier this week that after construction is completed, county officials will examine what, if anything, went wrong. He said that Foulger-Pratt would provide any additional funding needed to fix the cement problem.