Two women smoke cannabis vape pens at a party in Los Angeles. (File photo: AP)

Health officials say their investigation into a recent outbreak of severe vaping-related illnesses is increasingly focused on products that contain THC.

The Centers for Disease Control and Prevention said Friday most people who got sick vaped THC, the ingredient that produces a high in marijuana.

A new study published by CDC found two-thirds who got sick in Illinois and Wisconsin said they vaped prefilled THC cartridges from one brand.

The investigation is ongoing. No single device, ingredient or additive has been identified.

The ailment has sickened at least 805 people, from 46 states and one US territory. Thirteen deaths have been reported, from 10 states.