keisatu ga genin wo tokuteisita.

It is read:

けいさつ が げんいん を とくていした。

Word by word:

• 警察 = けいさつ = police
• 原因 = げんいん = cause
• 特定した = とくていした = identified / determined

In normal Japanese writing, it would usually appear without spaces:

警察が原因を特定した。

警察 means the police as an institution or organization.

Like the police in English, it does not have to clearly show singular vs. plural in the same way that a regular count noun does. In this sentence, it simply means that the police identified the cause.

So you should not think of it as necessarily a police officer. If you wanted to say a police officer, you would use something like 警察官.

Here, が marks 警察 as the grammatical subject of the sentence.

So:

• 警察が = the police are the ones who did the action
• 原因を = the thing that was identified
• 特定した = identified

A natural way to understand the structure is:

[The police] [identified] [the cause].

Japanese often uses が when introducing or focusing on who did it.

Both are possible in some contexts, but they feel different.

• 警察が原因を特定した。
  This focuses more on the police as the subject, or simply presents the event as new information.

• 警察は原因を特定した。
  This makes the police the topic, often with a nuance like as for the police, they identified the cause.

So が is often used when you are just reporting what happened, especially in news-like statements.

A rough comparison:

• 警察が原因を特定した。 = The police identified the cause.
• 警察は原因を特定した。 = The police, at least, identified the cause. / As for the police, they identified the cause.

を marks the direct object of the verb.

Here:

• 原因を = the cause is the thing being identified

So 特定する is acting on 原因.

This is very similar to English word order in meaning:

• subject: 警察
• object: 原因
• verb: 特定した

The dictionary form is 特定する.

This is a する-verb noun + する combination:

• 特定 = identification / specification
• 特定する = to identify / to determine

Then:

• 特定する → non-past
• 特定した → past

So 特定した means identified or determined.

Because the sentence is reporting a completed action:

The police identified the cause.

Japanese past tense often covers what English expresses as simple past:

• 特定した = identified / determined

In news writing, Japanese often uses the plain past form to report an event that has already happened.

Not exactly.

特定した is more formal and precise. It means something like:

• identified
• determined
• pinpointed

So this sentence sounds more official or factual than a casual phrase like found out.

For example, in a police or news context, 特定した is very natural because it suggests that the cause was established or confirmed.

原因 means cause.

It is close to reason, but not always the same.

• 原因 = the cause of something, often in a factual or physical sense
• 理由 = reason, often explaining motive or justification

For example:

• 火事の原因 = the cause of the fire
• 遅れた理由 = the reason for being late

So in this sentence, 原因 is the correct word if the police identified what caused an event.

Yes, Japanese word order is more flexible than English, as long as the particles stay the same.

For example, these can mean basically the same thing:

• 警察が原因を特定した。
• 原因を警察が特定した。

Because the particles show the roles:

• が = subject
• を = object

However, changing the order can change emphasis. The most neutral order here is:

警察が原因を特定した。

Yes, it is fairly formal or neutral, and it sounds very natural in writing, reports, or news.

Reasons:

• 特定する is a formal verb
• the sentence uses plain form, which is common in written reports
• the vocabulary is not casual conversation vocabulary

In casual speech, someone might use a less formal expression depending on context, but for police reports or news, this sentence sounds very natural.

Yes. A polite version would be:

警察が原因を特定しました。

The difference is:

• 特定した = plain past
• 特定しました = polite past

The meaning is the same, but しました is appropriate in polite speech or formal conversation.

Sometimes, yes. For example:

原因が特定された。

This means:

The cause was identified.

That version focuses on the result rather than on who identified it.

So:

• 警察が原因を特定した。 = focuses on the police doing the identifying
• 原因が特定された。 = focuses on the cause having been identified

Both are natural, but they highlight different things.

They are probably included only for learners, to make the parts easier to see:

• 警察
• が
• 原因
• を
• 特定した

In normal Japanese writing, you usually do not put spaces between words, so it would be written as:

警察が原因を特定した。

Japanese relies on kanji, kana, and context rather than spaces to show word boundaries.