Washington (CNN) -- A Georgetown University student was charged on Friday with possessing ricin after admitting he made the poison in his campus dorm room, a court document showed.
Daniel Harry Milzman, 19, appeared in federal court, where a judge ordered him held pending a hearing next week.
Milzman was arrested by the FBI and charged with possessing a biological toxin, according to an FBI affidavit.
That submission said he learned how to make ricin on his iPhone and then bought ingredients at retail stores.
Ricin is a deadly toxin derived from castor beans that has no known antidote.
On Monday, Milzman allegedly showed a bag that he claimed to contain ricin to his dorm adviser, who notified school authorities. They in turn called police, the filing states.
Preliminary lab tests confirmed the substance was ricin, it said.
Milzman allegedly produced the substance a month earlier in his room, placed it in plastic bags sealed with hockey tape and stored it in his room, according to the document.
The amount produced possibly could have been enough to kill someone had it been inhaled or injected, the affidavit said.
Milzman is due back in court on Tuesday
His attorney, Danny Onorato, declined comment when contacted by CNN on Friday evening.
Georgetown said in a statement on Wednesday that tests on McCarthy Hall for the presence of biological agents were negative, and there had been no reports of anyone being exposed to ricin.
The university on Friday said the undergraduate student will not be permitted to return to campus at this time.
"The possession or manufacturing of illegal substances are issues we take very seriously and are violations of the university's student code of conduct," said media relations director Rachel Pugh in a statement.
CNN's Greg Seaby contributed to this report.