The exact mechanisms of these interactions are still under investigation.

Again, the exact mechanisms that control this are still only partially known.

The exact mechanism of its action is not yet known.

The exact mechanism for this process was not explained in the paper.

However, in many cases, the exact mechanism of killing is not known.

"I am not sure of the exact mechanism, but we all know the Americans have very sophisticated technology."

I am not sure that the exact mechanism is well understood.

The exact mechanism of these effects is not yet known.

But the exact mechanism of its functioning is not known to all.

The exact mechanisms for this color change, however, remains unknown.