Collocations for investigate - verb

carefully, closely, in detail
extensively
adequately, fully, properly, thoroughly
The allegations have not yet been properly investigated.

actively, vigorously
He claimed the Army had failed to vigorously investigate the case.

empirically, experimentally, rigorously, scientifically
further

ask sb to, be called in to
Police have been called in to investigate the complaints.

decide to
agree to, pledge to (esp. BrE), promise to
The company has promised to investigate claims that its products are unsafe.

aim to, be designed to, seek to

for
He is being investigated for illegal business dealings.

Investigate is used with these nouns as the subject:
detective, enquiry, journalist, jury, officer, panel, police, prosecutor, research, researcher, study

Investigate is used with these nouns as the object:
abuse, affair, allegation, aspect, case, cause, charge, claim, complaint, corruption, crime, death, disappearance, distribution, effect, effectiveness, extent, feasibility, impact, incidence, incident, influence, irregularity, link, matter, mechanism, misuse, murder, nature, origin, phenomenon, possibility, problem, relationship, report, role, scandal, sighting, subject, utility, validity, violation, workings