Twenty-two Chinese nationals were in custody Wednesday after they apparently let themselves out of a 40-foot cargo container that had been used to smuggle them from China, officials said.

The 18 men and four women, all believed to be in their 20s and 30s, seemed to be in good physical condition after about two weeks in the container, said Michael Milne, a spokesman for U.S. Customs and Border Protection.

Port of Seattle security guards spotted the group about 1 a.m.

Milne said there was no evidence of "any real criminal or terrorist activity ... just an alien smuggling operation."

Milne said the stowaways had not told investigators how much they paid for the voyage. He said it could take investigators several days to determine whether they'll be deported, be held as material witnesses or face other proceedings such as asylum hearings.

The container, the second from the bottom in a stack of four, had been flagged for a special examination but that had not been conducted before the group was caught, Milne said. He would not reveal why the container had been flagged.

The container had been loaded on the ship in Shanghai and had water bottles, food, blankets and toilet facilities.

"The conditions are certainly not deluxe, but everyone came off in apparently good health," Milne said.

The group apparently pried the container open early Wednesday and lowered themselves about seven feet to the ground, he said. About half were found within the terminal and the other half were spotted trying to get out through a gate, Milne said.

Once they were intercepted, "there was no attempt to flee or hide," he said. "They were cooperative."

It was believed to be the first detection of a human smuggling attempt via cargo container in Seattle since a flurry along the U.S. and Canadian West Coast in 2000 and 2001. Almost all of those caught were deported. Three found in a shipping container had died before reaching Seattle in January 2000.

Milne said he didn't yet know who owned the ship, which was registered in Liberia.