The Drug Enforcement Agency has apologized for its agents forgetting about a college student who was rounded up in a raid last month and left jailed for five days without food, water or access to the toilet.

DEA San Diego Acting Special Agent-In-Charge William Sherman said in a statement that he was troubled by the treatment of Daniel Chong and extended his "deepest apologies" to him, the Associated Press reports.

The DEA is investigating how the 24-year-old was forgotten while other suspects in the April 21 roundup were released.

Chong, an engineering student at the University of California-San Diego, was never arrested, was not going to be charged with a crime and should have been released, a law enforcement official who was briefed on the DEA case tells the Associated Press.

He was among nine students swept up in the raid by DEA agents from its Kearny Mesa field office, the San Diego Union-Tribune reports. The sweep netted 18,000 Ecstasy pills, other drugs and weapons.

Chong says he had been told during an initial interview after the raid that he had been in the wrong place at the wrong time and would be released shortly. One agent even promised to drive him home, Chong tells the newspaper.

Instead, he was returned to his 5-by-1o-foot windowless holding cell to await his release. The door swung closed sometime that Saturday and didn't open again until Wednesday. Chong said he was in one of the middle cells, with no toilet and no water, the newspaper reports.

"I had to recycle my own urine," Chong says. "I had to do what I had to do to survive."

He says he also remembers biting his eyeglasses and using the broken shards to scrawl a note "Sorry, Mom" onto his left arm.

Chong was eventually set free and rushed to a nearby hospital, where he spent five more days recovering from problems including a perforated lung that was the result of eating broken glass, the Union-Tribune reports.