Police have not said what might have motivated the poisoning.

The Alameda County district attorney’s office charged Xu on Thursday with premeditated attempted murder resulting in great bodily injury, according to court records.

Xu has also been charged with two other counts of felony poisoning “which may have caused death and which did cause the infliction of great bodily injury."

As of Monday, Xu remained in custody and was being held without bail. His arraignment is set for Tuesday morning at Wiley Manuel Courthouse in Oakland.

Xu, who received his undergraduate and graduate degrees from UC Berkeley, was the principal engineer at Berkeley Engineering and Research (BEAR), where he’s worked since 2009, according to historical online search records.

In 2013, BEAR published a notice in the San Francisco Business Times announcing that Xu had passed the state’s engineering examination and identifying him as its head metallurgist, a kind of scientist who works with metals.

Xu, who lives in Lafayette, ran a materials and metallurgy lab at BEAR. In a promotional statement previously posted on the company’s website, he wrote, “With our extensive knowledge in physics, engineering (materials, mechanical and electrical), and experience in testifying, we can solve and explain almost any problem or failure.”

BEAR did not respond on Monday to requests for comment.

Xu was quoted widely in 2013 in connection with the failure of seismic safety bolts used to build the San Francisco-Oakland Bay Bridge. A number of media sources asked him to discuss the metallic properties of the bolts and weigh in on safety concerns.

According to an earlier version of his resume, Xu also did testing in connection with the San Bruno pipeline explosion in 2010 and offered his services as an expert witness for depositions and trials, charging $350 an hour.

Cadmium is a metal found in the earth’s crust that’s primarily used in batteries, according to the National Center for Biotechnology Information.

“Eating food or drinking water with very high cadmium levels severely irritates the stomach, leading to vomiting and diarrhea, and sometimes death,” the agency wrote.

Exposure to lower levels of the metal over prolonged periods can also cause kidney damage and make bones become fragile and break more easily.

This article originally appeared in Berkeleyside.