Calhoun County authorities tell WBCK the local man afflicted with Thallium poisoning continues to improve, though he has not been well enough to aid investigators as they try and figure out how he became poisoned.

Sheriff Matt Saxton said the man was already ill and in a coma when the investigation began, so lacking input from the victim meant the investigation had to go in a broader direction. The effort has netted no specific leads as to the cause of the poisoning.

County Health Officer Jim Rutherford said there is, on average, one Thallium case per year in the United States. Recently, there have been two confirmed cases in Michigan, including the Battle Creek case.

Click the player below to hear details on the investigation and Thallium's origins and potential causes.

Hear The Richard Piet Show weekday mornings from 5:30-9 on WBCK.