UPDATE: A 4m-long shark has bitten off a scuba diver's fins off a Perth beach.
The incident was reported at 10.55am just off Little Island, which is north of Hillarys Yacht Club, the Department of Fisheries said.
The diver was "OK", the department said.
According to reports, he will not be returning to the water for "a while".
A Whitfords Sea Rescue spokesman said two free divers informed rescue crews of their close encounter on their way back to shore.
"Our guys were just leaving Hillarys to pick up a vessel that needed towing and they came across two guys, who told them about what happened," the spokesman said.
"Apparently, one of the guys had part of his fin bitten off by a shark."
Rescue crews did not attend the scene of the attack.
The spokesman said the men were "pretty shaken up".
The Westpac Helicopter was sent to Little Island, Surf Life Saving WA tweeted.
It was unable to find the shark and returned to base.
"Beach-goers advised to take additional caution in the Hillarys area," SLSWA tweeted.
It is understood that a Whitfords Volunteer Sea Rescue vessel has been used to warn people on boats about the shark.
SLSWA said beach-goers all the way from Marmion Anglers Club to Mullaloo Beach are being warned by lifesavers to take extra care in the water.
The warning comes after swimmers were this morning urged to check with authorities before hitting the water after a great white shark was spotted.
SLSWA reported a tagged white shark off Scarborough Beach about 7.30am.
Beach inspectors closed Scarborough, Floreat and City beaches, but re-opened them soon after.