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Preposition before noun

How do you use investigation with prepositions?

Under investigation is a fixed and common expression. Of investigation usually appears only inside longer noun phrases.

Quick answer

Most common pattern

Use under investigation to mean that someone or something is being officially examined. Of investigation is not normally used as a fixed phrase, though of can connect investigation to another noun, such as results of the investigation.

The company is under investigation.
He remains under investigation for fraud.
The findings of the investigation were published.

Choose the pattern by meaning

These forms are not interchangeable. Choose the construction by meaning, not by which preposition appears most often.

1
under investigation

Showing active official examination

Use under investigation for ongoing police, legal, or formal inquiries.

Several officials are under investigation.
The incident is under investigation by regulators.
2
investigation into + topic

Naming what is being investigated

Use into for the subject or issue examined.

investigation into data leaks
investigation into the accident
3
of the investigation

Referring to parts or results of an investigation

Of links investigation to another noun rather than forming a fixed phrase with investigation itself.

The scope of the investigation expanded.
Witnesses discussed the outcome of the investigation.

See the difference in context

The same subject can take different constructions because each sentence answers a different question.

Construction
Example
Meaning
under investigation
The factory is under investigation.
Standard fixed expression for active inquiry.
of investigation
The purpose of the investigation was unclear.
Of usually belongs to a larger noun phrase.
investigation into
Police opened an investigation into the fire.
Standard for the subject investigated.

Common mistakes

Some combinations appear in real text but do not mean what learners often assume.

Using of investigation as a standalone phrase

English normally uses investigation with into or under investigation instead.

✕ The case is of investigation. ✓ The case is under investigation.

Confusing under investigation with investigation of

Investigation of is possible in formal writing, but under investigation describes status.

✕ The company is investigation of fraud. ✓ The company is under investigation for fraud.

Omitting the article in of phrases

Of phrases usually need another noun and often an article.

✓ The findings of the investigation were released.

Quick practice

Choose the expression that matches the intended meaning.

1. The airline is currently ___ investigation.
2. Police launched an investigation ___ the explosion.
3. The results ___ the investigation were surprising.

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Frequently asked questions

Is under investigation formal?

Yes, it is common in legal, police, and news contexts.

Can I say investigation of?

Yes. Investigation of something is grammatical, especially in formal writing, but it has a different structure from under investigation.

Why is of investigation uncommon alone?

Because of usually needs another noun before investigation, such as details of the investigation.

of, about, against, to or for racism? of, about, for, in or on friendship? of, about, for, on or to thing? of, about, for, to or with sex? of, about, on, to or for moon? "of access" or "with access"? "of accommodation" or "for accommodation"? "of accuracy" or "for accuracy"? "of action" or "in action"? "of actor", "with actor" or "by actor"? "of address" or "to address"? "of administration" or "in administration"?

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