A project to collect health data on millions of patients without their or their doctor's knowledge is drawing scrutiny from Federal regulators, a report Tuesday said.

The so-called "Project Nightingale" between Alphabet's (GOOG) - Get Report Google unit and hospital operator Ascension gained attention Tuesday after a report in The Wall Street Journal said data was being collected without patient knowledge or consent.

Jim Cramer: Here's Why 'Project Nightingale' Is Bad News For Google.

The office of Civil Rights at the Department of Health and Human Services has launched a probe of the project, the Journal reported late Tuesday. The investigation "will seek to learn more information about this mass collection of individuals' medical records to ensure that HIPAA protections were fully implemented," director Roger Severino told the paper in a statement.

Shares of Alphabet fell $2.40, or 0.18%, to $1,296.40 in after-hours trading.