HONG KONG — Han Dong was operating a crane in China’s rust belt last August when he heard about a chance to make it big in America.

Local recruiters told him he could make as much as $2,900 a month, or nearly four times the average wage in China — and could even eventually apply for an American green card.

Instead, Mr. Han said, he ended up working on the construction site of a casino on Saipan, part of an American commonwealth in the Pacific Ocean, where federal officials are investigating working conditions at a project managed by Chinese construction firms. An American green card, which would allow him to be employed legally there or anywhere in the United States, no longer appears very likely.

“They tricked us to come here,” Mr. Han said of the agents that transported him to Saipan, where he put up scaffolding for 12 hours a day in the tropical heat. Before the fees he paid out to middlemen to get hired, he made only half what he was promised, he said.