The exact extent of the crackdown is unclear, since most high-level investigations are kept under wraps.

He said news reports had led him to order a high-level investigation.

A high-level investigation was begun to determine the source of the leak.

The American command in Baghdad announced a high-level investigation.

The American command here has opened a high-level investigation of the incident.

Hours later, the American command in Baghdad announced that it was opening a high-level investigation into the incident.

Criticism also focused on the fact that it took five weeks to order a high-level investigation into the events in Somalia.

The shutdown did not result in any supply issues, but the incident triggered a high-level investigation.

He said that news reports of the tragedy last week had led him to order a high-level investigation.

The Times article prompted a high-level investigation to find the sources of the leak, according to a person familiar with the investigation.