Kilauea Volcano continues to emit sulfur at potentially unhealthy levels long after its active eruption ended in September 2018, a team of students from MIT has found.

The team presented its findings on Thursday, West Hawaii Today reported.

The students were part of MIT’s Traveling Research Environmental eXperiences (TREX) program, which gives undergraduates research opportunities over winter break.

The 14 students, along with three teaching assistants and two professors, established a home base in Mountain View, and set up a sensor about 100 yards from Kilauea’s fissure 8. They recorded sulfur dioxide levels from Jan. 16 to 22, along with humidity, temperature and wind direction.

Their data showed levels peaked on Jan. 18 at 113.4 parts per billion. The EPA sets the maximum safe level at 75 ppb.