Usually I feed my European pond turtles near the tank but it happened that I had to take them to the kitchen. The gas cooker was on and the turtles probably sensed close fire and tried to escape the bowl I brought them in (usuallu they don't do that). What else are turtles afraid of?
Turtles as well as other animals can be afraid of everything different from their natural habitat. Any tank is an unnatural habitat and even if the turtle can get used to it, any sudden movements outside the tank, loud noises, knocking on the tank wall etc can scare it. This fearfulness has helped animals to survive for thousands of years, it's a totally natural reaction. Of course your turtles could be scared of fire. Wild animals always try to run away from fire. I'd really try to be more cautious next time to reduce their stress.