The FCC said today that it will investigate whether “major carriers” provided inaccurate information on their coverage areas as the agency determined where to send funds for rural broadband.

The Mobility Fund II project is meant to allocate more than $4.5 billion to encourage building out mobile broadband service in rural areas. As part of the project, the FCC requested coverage maps from carriers, which it could then use to determine which areas needed support.

The agency said a review of more than 20 million speeds tests raised serious questions about the accuracy of the data, and it has suspended the next steps of the project while it investigates.

FCC Chairman Ajit Pai has said improving rural access to broadband has been a key goal for the agency. But the FCC has faced criticism over its maps in the past, most recently after a report from Microsoft found broadband access was less widespread than the agency’s numbers suggested.

Pai said in a statement that the agency’s preliminary review of the mobile coverage data “suggested significant violations of the Commission’s rules.”

“That’s why I’ve ordered an investigation into these matters,” Pai said. “We must ensure that the data is accurate before we can proceed.” No carriers were mentioned by name in the statement.