Daniel Chong faced no charges but was seemingly forgotten and endured four days locked up in isolation without food or water

A 25-year-old college student has reached a US$4.1m settlement with the US government after he was abandoned in a windowless cell for more than four days without food or water.

Daniel Chong told how he drank his own urine to stay alive, hallucinated that agents were trying to poison him with gases through the vents and tried to carve a farewell message to his mother in his arm.

It remained unclear how the situation occurred and no one had been disciplined, said Eugene Iredale, an attorney for Chong. The justice department's inspector general is investigating.

"It sounded like it was an accident – a really, really bad, horrible accident," Chong said.

Chong had been taken into custody during a drug raid and placed in the cell in April 2012 by a police officer authorised to perform Drug Enforcement Administration work. According to Iredale the officer told Chong he would not be charged and said: "'Hang tight, we'll come get you in a minute." Chong ended up being abandoned there.

Chong said he began to hallucinate on the third day in the cell. He urinated on a metal bench so he could have something to drink. With cuffed hands he stacked a blanket, his trousers and shoes on a bench and tried to reach an overhead fire sprinkler so he could set it off.

Chong said he accepted the possibility of death. He bit into his eyeglasses to break them and used a shard of glass to try to carve "Sorry Mom" on to his arm. He only managed to finish an S.

He slid a shoelace under the door and screamed to get attention before five or six people found him covered in his faeces in the cell. "All I wanted was my sanity," Chong said. "I wasn't making any sense."

Chong was in hospital for five days for dehydration, kidney failure, cramps and a perforated oesophagus. He lost 15lb in weight (7kg).

Chong, then a 23-year-old engineering student, had been at a friend's house where the DEA found 18,000 ecstasy pills, other drugs and weapons. Iredale acknowledged Chong had been there to consume marijuana. He and eight other people were taken into custody. Authorities had questioned and decided against charging him before he was left in the cell.

The DEA issued a rare public apology and introduced national detention standards including daily inspections and a requirement for cameras in cells, said Julia Yoo, one of Chong's lawyers.

Justice department spokeswoman Allison Price confirmed the settlement was reached for $4.1m but declined to answer other questions. The DEA didn't immediately respond to a request for comment.