Pieces from the sub, which imploded on a deep dive to the Titanic, were unloaded in St John's, Canada, on Wednesday.
Officials say the sub's landing frame and a rear cover were found among the debris.
US medical professionals will conduct a formal analysis of presumed remains, the coast guard said in a statement.
The agency is in the early stages of an investigation into the causes of the disaster. The Coast Guard's Marine Board of Investigation (MBI) will transport the evidence to a US port for further analysis and testing.
