SAN FRANCISCO — When Google first revealed in 2010 that cars it was using to map streets were also sweeping up sensitive personal information from wireless home networks, it called the data collection a mistake. On Saturday, federal regulators charged that Google had “deliberately impeded and delayed” an investigation into the data collection and ordered a $25,000 fine on the search giant.

The finding, by the Federal Communications Commission, and the exasperated tone of the report were in marked contrast to the resolution of a separate inquiry two years ago. That investigation, by the Federal Trade Commission, accepted Google’s explanation that it was “mortified by what happened” while collecting information for its Street View project, and its promise to impose internal controls.

But since then, the F.C.C. said, Google repeatedly failed to respond to requests for e-mails and other information and refused to identify the employees involved.

“Although a world leader in digital search capability, Google took the position that searching its employees’ e-mail ‘would be a time-consuming and burdensome task,’ ” the report said. The commission also noted that Google stymied its efforts to learn more about the data collection because its main architect, an engineer who was not identified, had invoked his Fifth Amendment right against self-incrimination.