A University of California student who went "completely insane" after Drug Enforcement Administration agents accidentally left him alone in a cell for five days has sued the agency for $20 million.

Daniel Chong, 23, filed the claim against the DEA on Thursday, a day after the agency's San Diego office apologized to him, reports the Los Angeles Times. The lawsuit claims the treatment constitutes torture.

Chong, who was detained in an April 20 drug sting, spent three days in the intensive-care unit and is still recovering from his ordeal. Here's an excerpt, courtesy of CBS News:

The student said he ingested a white powder that he found in the cell. Agents later identified it as methamphetamine. Chong said he ingested it to survive. The next day, hallucinations started, he said. They included Japanese animation characters who told him to dig into the walls to search for water, which he tried, tearing apart the wall's plastic lining.

Chong was handcuffed during the raid, but told by agent that he would be released.