Cause of incidents in the pool with 原因
Kanji Explanation: Causes and dependence with 因

After cheerleading practice, Sakura overhears her friends talking about incidents at the school pool, where Sakura and Chiharu were among those mysteriously pulled underwater.
- 千春:
- 「きょう また プールで足
( 引( っぱられておぼれそうになったんだって」- “I heard that today, someone got dragged under the water at the pool and almost drowned again.”
- 奈緒子
( : - 「こわいねーーー」
- “That's scary!”
- 千春
( : - 「先生
( が原因( がわからないならプール閉鎖( するしかないっていってたよ」- “The teacher said that if they can't figure out the cause, they'll have no choice but to close the pool.”
Key Points
原因
( = “cause” behind a problemHere 原因
( means the cause of the pool incidents, explaining why students keep getting pulled underwater.
原因
( がわからないなら = if the cause is unknown原因
( がわからない literally says “the cause is not known”.The English translation makes the implied investigators explicit as “they can’t figure out the caused”.
Two different が markers
In 先生
( が…っていってた, the first が marks the teacher as the one who said it.In 原因
( がわからない, the second が marks 原因( as what is unknown.
閉鎖
( するしかない = have no choice but to closeプール閉鎖
( する is “to close the pool”, using 閉鎖( with する as a verb.〜するしかない means there is no option except doing that action.
Casual reported speech with っていってた
っていってた is casual と言
( っていた, reporting what the teacher said.