The number of vaping-related lung illnesses in the US is now at 530, an increase of 150 cases since last week, according to an update by the CDC.

The CDC has ramped up its investigation, activating its Emergency Operations Center this week in an effort to nail down the cause of the illnesses, which remains unclear. In addition, the Food and Drug Administration has enlisted the help of its office of criminal investigations, the law enforcement arm of FDA.

So far, it appears that most patients have fallen ill after vaping THC — a psychoactive component in cannabis — nicotine or a combination of both. Symptoms include severe pneumonia, in many cases. Patients can recover from the acute problem that led them to the hospital, but long-term impacts are unknown.