Published: Feb 19, 2011 6:01 PM EST
Updated: Feb 19, 2011 3:01 PM EST

WEST PALM BEACH, Fla. (AP) - Huge schools of sharks are being spotted off of South Florida as they migrate north.

The blacktip and spinner sharks have been most visible off Palm Beach County as they migrate from the Caribbean.

Officials say they're generally not aggressive, but that the threat of bites still exists for swimmers.

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