MONROE — When Xiaoye Wang checked into a Princeton hospital last month, his case appeared to be routine. The computer engineer from Monroe Township complained only of flu-like symptoms, authorities say.

But for nearly two weeks, Wang struggled to get better. On Jan. 25, after a series of tests, doctors discovered the reason: Wang had been poisoned with thallium, a highly toxic metal.

He died in his hospital bed the following day. And today, following an investigation that brought in the FBI and the State Police, authorities charged Wang’s wife, Tianle Li, with his murder.

A research chemist at Bristol-Myers Squibb since 2001, Li obtained an undisclosed amount of the radioactive substance, authorities say, and administered a dose to Wang in December or January.

Natives of China, Wang and Li moved to a new home on Stanley Drive in 2008 and had a son. But a year later, the marriage had soured, police say.

"The investigation determined that Li and Wang, who were in the process of getting a divorce, had been involved in a series of domestic disturbances since April 2009," Bruce Kaplan, the Middles*x County prosecutor, said in a press release.

Li’s attorney, Steve Altman, said his client is innocent.

"The divorce proceeding had been resolved in principle by a property settlement agreement," Altman said. "Mr. Wang was paying for support of his son. There was no motive for my client to kill her husband."

He said Li, who goes by the name Heidi, has no relatives in the United States. Their child, now 2, is in foster care, Altman said.

Li, 40, was first charged with hindering her own apprehension for giving false statements on Jan. 28, two days after her husband died in University Medical Center in Princeton, Kaplan said. The murder charge was lodged after an autopsy confirmed Wang was poisoned with thallium.

After searching the couple’s home in the southern end of Middles*x County, investigators concluded no one else had been exposed to the metal. Thallium, a radioactive substance, is used mostly in the electronics industry. It is also deployed in stress tests to diagnose heart disease.

For poisoning purposes, it would be in a powdery or crystallized state. The poison works by knocking out the body’s supply of potassium and attacking the nervous system, the stomach and the kidneys. Its effects can take weeks to kick in.

Li is being held in the Middles*x County Jail. Her bail was set at $150,000 on the hindering charge, but raised another $4 million after she was charged with murder.

Fred Egenolf, a spokesman for Bristol Myers Squibb, said the company would have no comment about Li.

Staff writer Rohan Mascarenhas and the Associated Press contributed to this report.