But some investigators question whether the science is ready for human experiments.

Pakistani investigators were present but did not question him, he said.

But many investigators questioned whether it would even be possible to do such a study.

Congressional investigators have questioned him about that several times in recent weeks.

Investigators for the safety board have been questioning members of the crew.

Investigators were questioning the men last evening, but no one was charged with a crime.

Investigators late last night were questioning another suspect in the shooting.

Since the son failed the test, investigators have questioned him again about his father's disappearance.

Last night, investigators were questioning a building resident about the accident.

He learned that investigators were questioning his colleagues and relatives.