Stephen Shankland/CNET

Google's partnership with Ascension, the second-largest health care system in the nation, over medical data has spurred a federal probe, according to a report Tuesday by the Wall Street Journal.

The Office for Civil Rights in the Department of Health and Human Services is opening an inquiry into Project Nightingale, an initiative that collects patient information from millions of Americans. That includes data on lab results, diagnoses and hospitalization records, and also includes patient names and birthdates. The purpose of the project is reportedly to design health software that could home in on a patient's medical history.

The US regulator "will seek to learn more information about this mass collection of individuals' medical records to ensure that HIPAA protections were fully implemented," office Director Roger Severino told the Journal. Severino referred to the Health Insurance Portability and Accountability Act, the federal law regulating the security and privacy of certain medical information.

HHS didn't immediately respond to a request for comment, and Ascension didn't comment on the HHS probe. Google acknowledged the federal inquiry.

"We are happy to cooperate with any questions about the project," Tariq Shaukat, president of Google Cloud, said in a blog post. "We believe Google's work with Ascension adheres to industry-wide regulations (including HIPAA) regarding patient data, and comes with strict guidance on data privacy, security, and usage."

When it comes to collecting medical information, Google has drawn scrutiny in the past. Two years ago, Google, the University of Chicago and an affiliated medical center struck a partnership that allowed the search giant to use patient data and health records in an attempt to improve predictive analysis. In July, Google, the university and the medical center were hit with a lawsuit after the medical center allegedly shared records with Google without stripping away identifiable information.

The federal inquiry also comes as Google signals a deeper investment in health services. Earlier this month, the search giant said it's buying Fitbit, a fitness tracker company, for $2.1 billion.

Originally published Nov. 12, 5:27 p.m. PT.

Update, 8:57 p.m.: Adds comment from Google.