Twenty-two Chinese nationals were in custody Wednesday after they apparently let themselves out of a 40-foot (12-meter) 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."

He said the stowaways were believed to be part of an organized smuggling ring, but he had no information about how much they paid for the voyage or who ran the operation.

Milne said it could take investigators several days to determine whether they people be deported, be held as material witnesses or face other proceedings, such as asylum hearings.

The shipping 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.

It 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."

The ship is owned by China Shipping Line, Milne said.

Officials at Norton Lilly, a Mobile, Alabama, company listed as China Shipping Line's agent in Seattle, did not immediately return a message seeking comment.

U.S. Sen. Patty Murray said the incident demonstrated the need for greater port security.

"This appears to have been a case of human smuggling, but that cargo container could have been filled with anything from a dirty bomb to a cell of terrorists," Murray said Wednesday in a speech on the Senate floor.

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.

Associated Press reporter Elizabeth M. Gillespie in Seattle contributed to this report.