Trois personnes manquent encore à l'appel.

[corgwin24]

English Translation

Three people are still missing.

manquer
manquer à l’appel =
(MILITAIRE) to be absent (at roll call)
(figuré & humoristique) to be missing
© Larousse 2014

[yottapolyglot]

You might also hear it after some sort of disaster took place (flood, earthquakes, fire) to mean that some people are still missing / unaccounted for.