GRANITE FALLS — A man believed to be in his 30s drowned Thursdaywhile floating on an innertube in the South Fork Stillaguamish River.

Bystanders saw the man in trouble and pulled him from the river, said Jim Haverfield, the Granite Falls fire chief.

That happened just after 1 p.m. near the 14300 block of Stehr Road, near Burn Road. The man apparently was using an intertube in a stretch of the river known for currents, Haverfield said. The man fell off the tube and went under.

It was not clear how long he was in the water, Haverfield said. Together, bystanders and firefighters provided CPR and other first aid for more than 30 minutes. Those efforts ultimately were unsuccessful.

The Snohomish County Medical Examiner’s Office is expected to determine and release the man’s identity. His name was not made public Thursday.