起火原因不明。

The cause of the fire is not known.

Source: Tatoeba

Sentence Composition

=1 起火 qǐhuǒ
  1. to catch fire
  2. to cook
  3. to get angry
=1 起火 qihuǒ
  1. (historical) a type of traditional Chinese firework
  2. a type of traditional Chinese firework
2 原因 yuányīn
  1. cause
  2. origin
  3. root cause
  4. reason

classifier: 個
3 不明 bùmíng
  1. not clear
  2. unknown
  3. to fail to understand