A California engineer accused of trying to poison his co-worker by spiking her food and water for more than a year was arrested and charged with attempted murder last week.

David Xu, an engineer at Berkeley Engineering and Research Inc., a consulting firm, is accused of adding the poisonous metal cadmium to co-worker Rong Yuan's food and water starting in October 2017, according to court documents filed in Alameda County last week. He kept trying to poison her through March of this year, the documents said.

For months, Yuan noticed that food and water she left unattended in her office had a strange taste and smell, the documents filed Thursday said.

She "reported suffering immediate and significant health problems after consuming this water and food, at times requiring emergency care at a hospital," the court filing said.

Yuan eventually viewed footage from a surveillance camera in her office and saw that Xu, 34, had added something to her water bottle on Feb. 11 and March 4, court documents said.

David Xu Berkeley Police Department

Two of Yuan's family members also allegedly reported getting sick in November and December of 2018 after drinking from the water bottle she had brought home from work.

Samples taken from the bottle tested positive for a toxic amount of cadmium, the court filing said. Blood samples also showed that Yuan and her two family members who drank the water had elevated levels of cadmium in their bodies.

Consuming cadmium, a blueish-white metal, "severely irritates the stomach, leading to vomiting and diarrhea, and sometimes death," according to the National Center for Biotechnology Information.

Exposure to the metal for a long period of time can also lead to kidney damage and bone fragility. Prosecutors said in the filing that exposure to cadmium can also cause cancer.

Xu was arrested last Thursday by Berkeley police and charged with premeditated attempted murder resulting in great bodily injury and two counts of felony poisoning, according to the Alameda County Sheriff's Office. He is being held without bail at a county jail and is due in court for a plea hearing Thursday.

Prosecutors didn't specify a motive for Xu's actions, and Berkeley police wouldn't comment on the case Wednesday.

Berkeley Engineering and Research did not immediately respond to a request for comment. The company lists 11 employees on its staff page, and Xu's name has been removed.

Yuan is an engineer at the company with a Ph.D. in materials science.