"This will be a long and extensive investigation," he said.

This was one of the most extensive investigations in our history.

But an extensive investigation has shown that the boys' story was true.

Also, it goes without saying that I have made my own extensive private investigations.

Despite extensive investigation, the police were unable to solve the crime.

Some couples never have a cause identified, often after extensive investigations.

Yet extensive investigations have failed to turn up a cause for the clusters.

The statement said the department had conducted an extensive investigation of the county's voting system.

An extensive psychiatric investigation of the family and their relationships is then indicated.

Certainly those diagnoses would not have justified more extensive investigation.