Three firefighters from Leatherhead went to hospital with suspected carbon monoxide poisoning after helping with flood relief along the Thames.
Yesterday the crew were called to Chertsey where flood victims have been evacuated in the face of rising flood waters.
Zane Gbangbola, 7, died on Saturday in Chertsey after he and his parents were taken unwell at their flooded home.
A Surrey Fire and Rescue spokeswoman said: "We can confirm that three of our firefighters were checked out at hospital last night as a precaution after feeling unwell following their shift.
"We are pleased to say that they are now absolutely fine. An investigation into the incident is continuing, and as yet there is no confirmation of the cause or the origin."
By phone the spokeswoman said: "The investigation has still not confirmed what the cause was. They went to hospital. They had gone home at the end of their shift and did not feel well."
Surrey Police have refused to be drawn on whether Zane Gbangbola suffered carbon monoxide poisoning.
Lee Duddy, Fire Brigades Union (FBU) representative in Chertsey, said he had not heard of any firefighters being taken ill last night.
He said: "We have been evacuating people from their homes. We got back from the station, got changed and went home."
More 500 properties have been flooded across the South East and communities are being warned against further flooding as the River Thames continues to rise.
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