They warn authorities to gird themselves for the possibility that many more men could surface.
I called the midwives at the hospital to warn them we might be on the way.
In the United States, people used to warn against taking wooden nickels.
Old English warnian "to give notice of impending danger," also intransitive, "to take heed," from West Germanic *warnojanan (cf. Old Norse varna "to admonish," Old High German warnon "to take heed," German warnen "to warn"); related to Old English wær "aware, cautious" (see wary). Related: Warned; warning.