34-year-old David Xu, a senior materials engineer and an alum of UC Berkeley, appeared in an Alameda County courtroom Thursday to enter a plea in a case in which he's accused of systematically poisoning a co-worker.

As KPIX/CBS SF reports, Superior Court Judge Delia Trevino set Xu's bail at $2 million following his not-guilty plea, saying she still could not be sure that Xu was not a danger to others. Xu's attorney, Julia Jayne, had been seeking $200,000 bail and presented multiple letters attesting to Xu's character.

Xu is accused of attempted to poison colleague and fellow engineer Rong Yuan. According to court documents, Yuan said she suspected Xu had been tampering with her food at the office and had experienced strange aftertastes, as well as extreme symptoms of poisoning. She also saw Xu on surveillance video putting a substance into her water bottle.

That substance has been identified as the toxic metal cadmium, and as the Chronicle reports, two of Yuan's relatives also tested positive for cadmium poisoning after sharing her water bottle after she brought it home from work. Cadmium is known to cause cancer, and per the Chronicle, its immediate affects can be diarrhea and vomiting. Extended exposure could lead to lung damage and kidney disease.

Berkeleyside first reported on Xu's arrest, which came last Thursday, March 28, at his home.

Xu and Yuan are employees at Berkeley Engineering and Research Inc.

Xu has been charged with attempted murder and two counts of felony poisoning. Police have yet to say what they believe Xu's motive was.