Google has released the Federal Communications Commission report with only private names redacted, the Los Angeles Times reported Saturday.
Google denies Street View project managers authorized the collection of personal data, which was based on code written in 2006.
The engineer who wrote the code said he told two other engineers about it and later reported to managers about it, as well. But managers said they ignored the engineer's report.
Later, the engineer asked a search quality team member about the data and was told "it had no use or value." After that, he dropped the idea, the report says.
The data collection was part of Google's effort to map wireless networks in a project connected to its "Street View" service, the newspaper said.
The personal data collected was "inadvertent" Google said, but the FCC said it had "significant questions" as to why Google collected the data.
During the investigation, the engineer declined to speak with the FCC directly, invoking the Fifth Amendment to the Constitution.
The FCC said Google did not break any laws, noting wiretapping laws under the Communications Act were written before WiFi technology existed.
Google was fined $25,000 for obstructing the investigation, although the company asserted the FCC caused the delays.
"While we disagree with some of the statements made in the document, we agree with the FCC's conclusion that we did not break the law. We hope that we can now put this matter behind us," Google said in a statement.