NEW YORK - The scientist at M.D. Anderson Cancer Center in Houston was hardly discreet. “Here is the bones and meet of what you want,” he wrote in a misspelled email to researchers in China.

Attached was a confidential research proposal, according to administrators at the center cited by the New York Times Monday. The scientist had access to the document only because he had been asked to review it for the National Institutes of Health — and the center had examined his email because federal officials had asked them to investigate him.

The N.I.H. and the F.B.I. have begun a vast effort to root out scientists who they say are stealing biomedical research for other countries from institutions across the United States. Almost all of the incidents they uncovered and that are under investigation involve scientists of Chinese descent, including naturalized American citizens, allegedly stealing for China.

Seventy-one institutions, including many of the most prestigious medical schools in the United States, are now investigating 180 individual cases involving potential theft of intellectual property. The cases began after the N.I.H., prompted by information provided by the F.B.I., sent 18,000 letters last year urging administrators who oversee government grants to be vigilant.

Nearly 200 investigations are underway at major academic centers. Critics fear that researchers of Chinese descent are being unfairly targeted.

So far, the N.I.H. has referred 24 cases in which there may be evidence of criminal activity to the inspector general’s office of the Department of Health and Human Services, which may turn over the cases for criminal prosecution. “It seems to be hitting every discipline in biomedical research,” said Dr. Michael Lauer, deputy director for extramural research at the N.I.H.

The investigations have fanned fears that China is exploiting the relative openness of the American scientific system to engage in wholesale economic espionage. At the same time, the scale of the dragnet has sent a tremor through the ranks of biomedical researchers, some of whom say ethnic Chinese scientists are being unfairly targeted for scrutiny as Washington’s geopolitical competition with Beijing intensifies.