The debris was discovered by a crew operating a remotely operated vehicle aboard the Horizon Arctic, a Canadian-flagged offshore tug and supply vessel.

Source: https://www.lacombeexpress.com/news/u-s-coast-guard-confirms-titan-debris-found-at-titanic-site-five-crew-dead/

"We are conducting a safety investigation in Canada given that this was a Canadian-flagged vessel that departed a Canadian port and was involved in this occurrence, albeit in international waters," said Kathy Fox, chair of the transportation board.

Source: https://abc11.com/titan-submersible-oceangate-us-coast-guard-titanic-explosion/13426606/