A former Lehigh University student accused of leaving racist graffiti for his roommate earlier this year is now accused of trying to kill the roommate by poisoning.

Yukai Yang was arraigned Thursday morning on charges of attempted homicide, aggravated assault, simple assault and reckless endangerment, after he turned himself in with his attorney, Janet Jackson, present.

Jackson did not return a phone message about the new charges. Yang was sent to Northampton County Prison in lieu of $200,000 bail.

At a news conference, Northampton County District Attorney John Morganelli said the two men were roommates for several years and were seniors at the time of the incidents this past spring.

Yang, a chemistry major at the time, is no longer a student at the university and his student visa has been revoked, prosecutors said. The roommate, Juwan Royal, graduated from Lehigh, but continues to suffer physical effects from the poisoning, prosecutors said.

Morganelli said it appears the poisoning occurred over a few months, with small amounts of thallium and possibly other chemicals mixed into food, drinks and mouthwash. The criminal charges are based on incidents where Royal was sick and there was a police response, but the district attorney said Royal had other incidents and symptoms that he had initially brushed off as just being sick.

“Initially, Mr. Royal was dumbfounded by this as everyone else, because he believed they had a fairly cordial relationship as roommates,” Assistant District Attorney Abe Kassis said.

The first incident involving police was back in February, when Royal said he drank from a water bottle in his room and felt burning in his mouth, according to Morganelli.

Royal woke up Yang and explained what happened, Morganelli said.

The pair rushed to the bathroom and, while Royal rinsed out his mouth, Yang reportedly said, “so the substance that they are putting in your drink is colorless, odorless and dissolves in water.”

Royal’s tongue was sore for a few days after the incident, Morganelli said.

Royal became ill again on March 18 and police were called, Morganelli said. Yang reportedly told officers he believed someone was tampering with items in the room and that the milk in the fridge and the Royal’s mouthwash had both changed color.

In the early morning of March 29, Royal became ill again, this time throwing up and shaking, Morganelli said. He was taken to a local hospital for treatment.

A week later, police were called to the pair’s room again, this time for the graffiti and damage to Royal’s TV and bed, Morganelli said.

Police seized Yang’s computer and cellphone after the incident.

After police began investigating the graffiti, the roommate reported the February incident and then submitted to a blood test, Morganelli said.

The victim’s blood tested positive for the toxic metal thallium, with 3.6 micrograms per liter, above the safe toxicity level for people, Morganelli said. Royal immediately started treatment for thallium poisoning.

Officers also found cadmium, another toxic metal, in the room, but Kassis said that was not present in Royal’s blood test results.

In an interview with investigators, Yang admitted to buying various chemicals on the internet, including thallium, with the intent to harm himself if he did poorly on future exams, according to Morganelli. Yang allegedly admitted mixing the chemicals with food and drinks in the shared fridge.

Yang, who turns 23 next week, was free on 10 percent of $10,000 bail in the graffiti case. He has a pretrial conference scheduled for Jan. 18 in the case.

In the graffiti case, police said in April black marker was used to write “(N-word) get out of here” in a university dorm room.

The victim said he left his room in Warren Square A and did not return until his roommate, Yang, reported the damage, police said.

Yang gave police a written statement, where he said he left the room after his roommate and locked the door. The room’s locks were changed and he was let back into the room by Lehigh police at 6:30 p.m., police said.

Police said they compared the written letter to the racist graffiti and saw similarities in the letters.

Yang was charged with ethnic intimidation, institutional vandalism and criminal mischief in that case.

“The Lehigh University Police Department has worked closely with the District Attorney’s Office on the investigation and will continue to do so. From the outset, our concern has been the health and safety of the victim of these alleged behaviors and, as such, Lehigh staff and faculty have been providing support, services and assistance,” Lehigh University spokeswoman Lori Friedman said in a released statement.

Sarah Cassi may be reached at scassi@lehighvalleylive.com. Follow her on Twitter @SarahCassi. Find lehighvalleylive.com on Facebook.