Food Safety News reports, public health officials in Amarillo, TX, are investigating a possible botulism outbreak after learning of four probable cases of the rare and potentially fatal foodborne illness on Friday, Dec. 6.

As of Wednesday, Dec. 11, officials reportedly had not yet identified a common source and were checking into what the four adult patients had eaten in the hours and days leading up to their illnesses. Two of the patients had been treated with botulism anti-toxin, and all four were hospitalized.

“All the patients are improving,” said Dr. Roger Smalligan, public health authority for Potter and Randall counties. “One patient required mechanical ventilation, but they’ve been taken off. Another is still on a ventilator, but is improving.”