In California, federal prosecutors have launched a criminal probe into Juul Labs, the immensely popular e-cigarette manufacturer, according to The Wall Street Journal. The focus of the probe is unclear, but the investigation is being led by the US Attorney’s Office for the Northern District of California, according to the Journal.

Juul has faced a number of legal challenges in recent months, as government outrage grows over hundreds of illnesses linked to e-cigarette use, including seven deaths.

A number of federal authorities are already investigating Juul. The Federal Trade Commission and a few state attorneys general are focusing on the company’s marketing practices and whether they purposefully sought to target minors. The Food and Drug Administration is also actively probing Juul, but little is known about its investigation.

The US Surgeon General declared vaping among minors an epidemic last year, and organizations like the Centers for Disease Control and Prevention have warned people to stop using e-cigarettes entirely as concerns over vape-induced illnesses have grown.

There’s also a looming federal ban on flavored vaping products generally. Earlier this month, President Donald Trump announced that his administration would seek to ban flavored vapes through the FDA, although the agency has yet to issue rule-making for the ban. “Not only is it a problem overall, but really specifically with respect for children,” Trump said at the time. “We may very well have to do something very, very strong about it.”

Juul did not immediately respond to a request for comment.