missing

アルジェリアの人質事件に関しての情報が錯綜している中、ことばを拾うのには若干のためらいがありますが、missingという単語についてひとくさり。

Hostages missing after Algeria raid on In Amenas plant

An Algerian army operation to free hostages at a gas facility in the desert has left a number of Islamist militants and their captives missing.

State TV said four foreign hostages had been killed in the raid. The militants had claimed to be holding 41.
Some hostages were freed, but the number of survivors was unconfirmed and UK officials said they were preparing for news of many British casualties.

Al-Qaeda-linked fighters occupied the facility near In Amenas on Wednesday.

http://www.bbc.co.uk/news/world-africa-21069727

この単語を私たちは、「（人が）行方不明で」など訳すことが多いと思いますが、このような文脈では「安否の確認ができていない」（unaccounted for）とすることもできます。（UG）