Since the rescue team entered the mountains, there has been no news at all.
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history
From 黄孝迈's Song-dynasty ci poem 《咏水仙》: 惊鸿去后,轻抛素袜,杳无音信 - the startled swan has flown, the silken stockings cast aside, no news at all. The 杳 evokes distance and darkness, like something lost to dusk.
usage
Specifically about a person (or a sent party - letter, expedition, inquiry) from whom all communication has ceased. Stronger than just 没消息 (no news), 杳 adds a sense of being swallowed by vastness.