About a thousand dead fish washed up onto a section of Old Orchard Beach on Friday afternoon, even as the popular resort town began a busy holiday weekend, authorities said.

The fish were spread over a large area south of the Old Orchard Beach pier near Union and Ocean avenues.

The Maine Department of Marine Resources says the fish are likely menhaden, also called pogies. The cause of the die-off is not yet known, but the department said the fish were either killed in a feeding frenzy by another fish, or killed by a commercial fishing operation that couldn’t get all of them into a boat, according to The Associated Press.

The silver fish are less than a foot long. Pogies are plentiful right now and sometimes wash ashore in large numbers in some parts of the Maine coast, although the fish are not a common sight on Old Orchard’s sandy shoreline.

Some beachgoers decided to stay out of the water, while others shrugged and swam anyway.

The town has been removing the fish as they wash onto the beach, a police dispatcher told News Center Maine (WCSH).