A patient in Illinois is the first to die of a mysterious lung illness linked to vaping, public health officials announced on Friday.

The death occurred as doctors and hospitals nationwide report an increasing number of vaping-related respiratory illnesses this summer: 193 cases have now been reported in 22 states, including 22 cases in Illinois, officials said.

[Update: Bronx teen’s vaping death is the youngest fatality in the U.S.]

They have been stumped in recent weeks by the cause. State investigators have not found a common link — other than vaping in general — among the patients turning up in emergency rooms.

Many patients, including some in Illinois, have acknowledged vaping of tetrahydrocannabinol, or (T.H.C.), the high-inducing chemical in marijuana, according to statements from federal and state health agencies.