The Katherine G., a spud barge, overturned at 9:46 a.m. as the crew was loading a crane aboard and preparing to cast off from Liberty Island, the Coast Guard and National Park Service said.
"Something happened that caused it to capsize," said Mindi Rambo, spokeswoman for the National Park Service.
A boat that was passing nearby pulled the two crew members out of the water, and the United States Park Police assisted with the rescue as well, according to the Coast Guard and the NYPD. One of the workers refused medical attention and the other was taken to a New Jersey hospital, Rambo said.
Their conditions were not immediately known.
David Burns, a retired fire official from West Hallam, England who was visiting the Statue of Liberty and Ellis Island, witnessed the accident and rescue.
"The left side [of the boat] went up, and the right didn't," Burns said. "And the whole lot collapsed. One of the guys was doing a lot of shouting because he was in shock. He was swearing a lot."
Burns saw one person removed on a stretcher.
Investigators were looking into why the barge overturned.
"We have a vessel on scene assessing the situation," said Charles Rowe, spokesman for the U.S. Coast Guard.
The crane that the boat was removing was part of theyearlong construction on the Statue of Liberty's pedestal, which is closed for renovations, Rambo said.