The Maritime and Coastguard Agency has said it responded to reports that sailors were struggling in the windy conditions, but that it is too early to tell how many people are involved in the incident in Strangford Lough.
A statement on the agency's website said:
The Coastguard is this afternoon coordinating a rescue response after approximately 80 sailing dinghies were hit by stormy weather in Strangford Lough.
Belfast Coastguard was first contacted just before 2pm reporting that some of the boats had capsized, while others were struggling to cope in the strong winds and squally showers.
The Bangor and Portaferry Coastguard Rescue Teams, the Portaferry and Newcastle RNLI lifeboats, the Irish Coast Guard helicopter along with the helicopter from RAF Valley have been sent to the scene.
It is not clear at this time how many people are involved and if there are any injuries. A search and rescue operation is ongoing.
More top news
Merrill Lynch has been fined £34.5 million for failing to report 68.5 million transactions, the Financial Conduct Authority has said.
Most people back a change in the law to ban unpaid internships that last for more than four weeks, a new poll suggests.
The favourites to win the Venice marathon finished behind a local runner - after they were led along the wrong route by a motorcycle guide.