SEATTLE -- Hundreds of hypodermic needles washed ashore in Seattle Thursday onto Alki Beach, where warm afternoon temperatures drew many people to the water. Officials closed the beach, calling the needles a "safety and health hazard."

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Police and firefighters were searching the beach for the needles, which were topped with orange caps and appeared not to have been used.

It wasn't clear where the needles came from, but the best guess was that they fell off a ship, KIRO 7 Eyewitness News reported.

Parks and Public Health -- Seattle & King County posted signs advising people to stay out of the water and away from the sand near the water.

The area affected is from approximately 49th Avenue SW to 61st Avenue SW.