The cause of the fire is still unknown.

飞机失火原因目前仍未所知。

youdao

The cause of the fire was unknown, and it was not clear how many of the injured were children.

火灾原因不明，也不清楚伤者当中有多少是儿童。

youdao

The cause of the fire in unknown.

这场火灾的起因还不知道。

youdao

The cause of the fire in unknown.

这场火灾的起因还不知道。

youdao