A spokesperson for a hotel in northwestern Minnesota said Sunday that its pool and spa area will remain closed for another 2½ weeks after four visitors contracted the potentially deadly Legionnaires' disease.

The people became ill between Jan. 22 and Jan. 27 after visiting the Crookston Inn and Convention Center, the Minnesota Department of Health announced Friday. The four were not overnight guests, but all visited the hotel for various occasions, the agency said in a statement.

State health investigators, who have not commented on the severity of illness of any of the four, are working with the hotel to determine the source of the bacteria.

"At this time, early evidence and past experience suggests the source of the infections is the hotel's spa," the statement said.

Spas are often found to be the source of Legionnaires' outbreaks due to their temperature and ability of the bacteria to travel in small water droplets.

Hotel management closed the spa and pool area to guests as it undergoes decontamination. A hotel staff member said Sunday the area will remain closed until roughly March 6.

The hotel is notifying guests for whom they have contact information who were at the hotel between Jan. 14 and Feb. 13 that they may have been exposed to the bacteria. Health investigators said it's possible other cases linked to the hotel could still emerge.

"If you spent time at the hotel between Jan. 14 and Feb. 13 and are ill with undiagnosed pneumonia or you develop symptoms in the two weeks following your visit, please see a health care provider to be evaluated for possible Legionnaires' disease," said Kris Ehresmann, the Health Department's director of the infectious disease division.

Legionnaires' disease is a bacterial pneumonia that can be severe. Symptoms can be deadly and include fever, fatigue, headache, muscle aches, chills, shortness of breath, loss of appetite and coughing.

The disease is spread by inhaling the fine spray from water sources containing the bacteria. It is not spread from person to person. Minnesota had more than 150 cases reported around the state last year.