EDGARTOWN, Mass. (AP) — Authorities in Massachusetts are warning swimmers about Portuguese men-of-war that have been spotted on Martha's Vineyard.

WCVB-TV reports the Edgartown Parks Department said in a Facebook post Thursday that the marine animals have washed up on South Beach.

The Portuguese man-of-war has a sail-like structure that enables it to float and long, dangling tentacles with powerful stinging cells. According to the National Ocean Service, man-of-war stings can be painful and cause welts on skin.

Experts say beachgoers should be careful because the animals can sting weeks after washing ashore.

___

Information from: WCVB-TV, http://www.thebostonchannel.com