UPDATE 5pm: MAIN Beach at Byron Bay has been reopened by lifeguards after the shark reported by a triple-0 caller earlier this afternoon was not seen again in the area.

Lifeguards conducted a patrol of the area on jetskis from Main Beach to Belongil, where the shark was reported cruising, but failed to confirm the initial sighting.

Duty officer with Surf Life Saving Far North Coast, Chris Samuels, said the beach had been reopened about an hour after the sighting.

INITIAL REPORT 2.20pm: BYRON Bay's Main Beach has been closed following reports of a shark sighting between The Wreck and Belongil Beach.

A triple-0 call by a member of the public reported the sighting about 1.20pm.

The closures comes after Ballina Shire Council announced all its beaches - from Seven Mile to South Ballina - would remain closed until at least 9am tomorrow.

Surf Life Saving Far North Coast duty officer Chris Samuels said lifeguards closed Main Beach following the shark sighting and were now patrolling the area in an attempt to verify the sighting.

There were reports of a shark chasing surfers between the Wollongbar wreck and Belongil.

"We're just taking precautionary measures at this stage," Mr Samuels said.

"If they give the all-clear than the beach will be reopened."

Police are also on the beach liaising with lifeguards in an attempt to verify the sighting. The beach is expected to reopen at 3pm unless there are further sightings.

In the event of a shark attack, all beaches in the vicinity are automatically closed for a minimum of 24 hours, however a shark sighting only requires a routine patrol of the area before the beach can be reopened on the discretion of lifesavers.

Ballina Shire Council said it expected the Skullcandy Oz Grom Open, which had to be cancelled today after an attack at Lennox Head this morning, to resume at 9am tomorrow. Extra air and water-base surveillance would be in place for the duration of the competition.