Firefighters were called out to a Rotherham playground after rubber matting around the play equipment was set alight.
The fire on Aughton Lane, Aston, was discovered at 7.40pm on Monday.
That same night crews also dealt with a rubbish fire started deliberately on Cooks Wood Road, Shirecliffe and grass torched on Dovecliffe Road, Wombwell, Barnsley.
Police were alerted to the incidents.
Witnesses or anyone with information should call police on 101.