(CNN)- The FDA is expanding its investigation into e-cigarettes.
The agency is now targeting 21 e-cigarette companies to find out if they been marketing products illegally.
The move comes less than two weeks after the FDA conducted a surprise inspection of e-cigarette maker Juul's Corporate Headquarters in San Francisco.
Agents seized thousands of documents, many relating to sales and marketing.
The investigations are part of the FDA’s crack-down on teen e-cigarette use.
- FDA expands e-cigarette investigation
- FDA reveals proposed graphic warnings for cigarette packs and ads
- US investigates seizure risk with electronic cigarettes
- High school e-cigarette use has jumped nearly 80%. Now, the FDA wants new regulations
- FDA warns consumers about e-cigarette liquids with erectile dysfunction drugs
- FDA anticipates EpiPen shortage
- 'It's not an eliminator, it's a reducer...' FDA expands the reach of HPV vaccine
- Brazil expands economic district
- Local medical group expands
- FDA approves preventive migraine treatment