The body of a man thought to be homeless was discovered Thursday morning when a worker opened a U-Haul trailer at the company's lot at King and Columbus streets, police said.

The man in the trailer was thought to have been dead since at least Tuesday, when people said they smelled a strong odor. "The scent would have knocked you out. I meant to check it out, but I didn't," passer-by Robert Pinckney said.

Police said a latch on the outside of the 5-foot-tall, 8-foot-long trailer's overhead door had been closed, sealing the man inside. U-Haul officials told police it's impossible for a trailer door to be latched accidentally by someone inside the trailer because of a safety device on the door.

Sgt. Mike Gordon said the middle-aged man, who had no identification on him, had no obvious signs of trauma. The man was found lying on a piece of cardboard, and his death appeared to be from natural causes. A glass coffee pot and a plastic cup were found in the trailer. An autopsy is planned, Gordon said.

"We may never learn how the trailer became locked. Hopefully, we'll have a cause of death by the autopsy," he said.

The U-Haul worker, who would not give his name, said he opened the door on the trailer at 9:25 a.m. Thursday as part of a routine inspection and found the dead man. "It scared the heck out of me," he said. The worker said he noticed the smell and blood on the ground but at first thought it was maybe a cat. Then he saw what looked like too much blood for a small animal.

Before discovery of the man's body, the unlocked rear doors of a row of nine trailers abutted a Columbus Street sidewalk. On Thursday afternoon, locks had been installed on the trailer doors, including the trailer where the man's body was found.

U-Haul's online trailer user manual says nothing about a risk of the trailer overhead door accidentally latching with someone inside. It says there is a risk of asphyxiation if someone rides in the trailer.

U-Haul corporate spokeswoman Joanne Fried said the trailer where the body was found had not been rented for more than a week "They do not self-lock. Someone would have to be outside to lock it. It's a bizarre situation," she said.

Charleston Interfaith Crisis Ministries Executive Director Stacey Denaux said it was troubling that homeless people could crawl into open trailers. She likened it to the dangers of kids climbing into abandoned refrigerators. "I would assume businesses like that would lock the trailers," she said.

At the shelter, a man who identified himself as Donald said he had slept in a U-Haul trailer in Columbia. "There's no way to lock yourself in. If he was locked in, somebody locked him in," he said.

Other homeless people said when the shelter reaches capacity, those without a place to stay go wherever they can to spend the night. "They sleep everywhere. They sleep in people's cars if they can get in the door," said a shelter resident.