In this task, given a sentence in the English language, your task is to convert it into the Japanese language.
One example: Test subjects will be administered either a placebo or PA-457 that will be taken in combination with the medication they already take.
Solution is here: 被験者は、彼らがすでに服用している薬剤と一緒に偽薬またはPA-457を与えられる。
Explanation: The above sentence is correctly translated from English to Japanese.

Now, solve this: The cause of the rock fall is unknown, but police have said that there had been no prior signs that the cliff was unstable.
Solution:
落石の原因は不明だが、警察は崖崩れが起こりそうな兆候は無かったと述べている。