Shark Sightings Close Cape Cod Beaches

The sightings of several great white sharks have prompted a swimming ban for the rest of the Labor Day weekend at some oceanside beaches in Massachusetts.

Officials at North Beach, Lighthouse Beach, South Beach and Hardings Beach in Chatham and Nauset Beach in Orleans put up red "no swimming" signs after a shark expert with the state Division of Marine Fisheries spotted four great whites off Chatham's coast Saturday.

State officials are also warning other swimmers in the area to be on the lookout for sharks this weekend.

The expert, senior biologist Gregory Skomal, and his crew were able to tag two of the sharks with electronic tracking devices. He says the sharks were 8 and 10 feet long.

Scientists told CBS Station WBZ it's the first time that great whites have been successfully tagged in the Atlantic Ocean.

"We had an incredible day today, and one I would never have anticipated," biologist Greg Skomal, heads of the state's Division of Marine Fisheries shark research program, told WBZ.

Crews aboard a spotter plane and a fishing vessel teamed up to find and tag the sharks over a period of about six hours.

The electronic tags' satellite-based technology will allow scientists to track the sharks' movements and better understand their migratory patterns.

Skomal said it is not unusual for sharks to be sighted at this time of year - as they are drawn to feed on the seal population - but he is surprised at the numbers spotted over the past few days.

He was able to tag a great white shark in 2004, but the tag didn't work properly. Skomal told WBZ he's been waiting a long time to find another great white.

"Ever since then I've been kind of like Ahab trying to track down my own great white," he said. "Today it happened, so I'm absolutely off the wall with happiness."