CLEVELAND (AP) — Officials investigating what sickened six passengers on a Frontier Airlines flight to Florida have shut down several drinking fountains at Cleveland’s airport.

The city of Cleveland says while it’s not known yet what caused the illnesses, Frontier Airlines reported that each of the sick passengers might have used a public drinking fountain before the flight.

Health officials removed the six passengers and held them for observation after their plane landed Tuesday at Tampa International Airport.

Authorities haven’t provided information on the symptoms passengers were experiencing or their conditions.

Officials in Cleveland said in a release Wednesday that the drinking fountains on Concourse A at Hopkins International Airport have been closed and sanitized.

They also say that water samples are being tested, but the results will take a day or two.