PIERRE, S.D. (AP) — South Dakota health officials say the number of vaping-related illnesses reported in the state has nearly doubled in the past two weeks.

The South Dakota Department of Health reports the number of cases jumped from six cases at the end of September to 11 cases as of Thursday. The patients range in age from 16 to 44 years old.

According to the Centers for Disease Control and Prevention, the number of vaping-related illnesses in the U.S. has now reached about 1,300 cases and at least 26 deaths.

Most who got sick said they vaped products containing THC, the marijuana ingredient that causes a high.

Last month, Sioux Falls health director Jill Franken urged people to follow the CDC’s recommendation to stop using e-cigarettes. The Oglala Sioux Tribal Council banned vaping on the Pine Ridge Indian Reservation.