The exact sources of the contaminated food are not yet known.

The team couldn't discover the exact source of the virus.

In individual cases, the exact source of any reported discharge may not be obvious without further investigation.

Until now he had not been able to check the exact source of the leak.

The exact source of the savings remains a bit unclear.

He said the exact source of the trouble had not been identified.

It is not clear what the exact source of conflict was at the time.

The exact source of these generic structures is not known.

Where the three lines crossed is the exact source of the sound.

The exact source of the town's name remains unknown today.