(CNN)Officials urged swimmers in Long Island, New York, to be cautious after at least four people were injured in suspected shark attacks this month.
"We are telling people that if they are swimming, they need to swim in lifeguard areas. They should only go waist deep and that they should be aware of their surroundings," Ocean Beach fire department chief Ian Levine told CNN on Thursday.
The warning comes after several shark attacks were reported since July 3 at beaches on Long Island, a large peninsula that stretches more than 120 miles to the east of New York City.
In the most recent attacks, a shark knocked a surfer off his paddleboard Wednesday morning at the Smith Point County Park beach, Suffolk County Executive Steve Bellone said during a news conference. The surfer suffered a bite on his leg before punching the shark and riding a wave to shore.
The beach was temporarily closed for several hours while officials scanned area waters for additional shark presence with drones, Bellone added.
Hours later, a shark bit a 49-year-old man in waist-high water off Fire Island after lifeguards had left the beach for the day, police said. The man walked out of the water and was later taken to a hospital via helicopter.
"He stated that he felt on his side a large animal rubbing against him. He went to move it away and that's when his hand got bit," Levine said.
On Thursday, a Fire Island state beach was closed briefly due to a shark sighting and reopened after a drone survey found no sharks, according to officials.
Bellone said shark activity closer to shore might be a new reality for beachgoers and safety officials.
"I think it is an indication, however, that what we're looking at is something of a new normal in that the sharks are -- these Tiger sharks are just a little bit closer to shore than they've been," he said. "They've always been out there, of course, you're interacting with marine life whenever you are out in the ocean, but they're closer to shore now. And those contacts -- those interactions with humans and shark may increase," Bellone said.
Earlier this month, two lifeguards were attacked by sharks while role-playing as victims during safety training drills.
Officials temporarily closed Smith Point County Park beach after a shark bit a 10-year veteran lifeguard on his chest and hand on July 3 during a training exercise. The beach was reopened in time for the July Fourth holiday after drone-scanning measures cleared the waters, Bellone told reporters at the time.
Another man training for an upcoming lifeguard test was attacked during a training exercise on July 8, less than a mile from the site of Wednesday's shark encounter.
"He was actually playing the victim and he was coming out to be rescued and I guess all his thrashing around caused the disturbance," Levine told CNN.