The historic Hudson River sloop Clearwater was removed from the Sail4th 250 Parade of Sail on Saturday morning after U.S. Coast Guard officials informed the vessel it had to leave the event's security exclusion zone because of advocacy banners displayed aboard, according to the organization that operates the ship.

The incident occurred around 11 a.m., shortly after the start of the parade in New York Harbor, Hudson River Sloop Clearwater said in a statement.

The Clearwater had been scheduled to escort the Portuguese Navy's sail training vessel, the NRP Sagres, a three-masted barque participating in the international celebration.

According to the organization, a U.S. Coast Guard vessel approached the Clearwater and notified Captain Rory Kane that the sloop had to exit the parade and leave the exclusion zone. Kane asked why the vessel was being removed and was told it was because banners displayed aboard read, "Save the Clean Water Act" and "Indigenous Rights, Racial Justice, Climate Solutions."

Jen Benson, Director of Advocacy for the Clearwater,  said a representative of Sail4th 250 told Kane that the decision to remove the vessel was "above their level."

The organization said the Clearwater would continue sailing south of the Verrazzano-Narrows Bridge until 3 p.m. with 29 passengers and 19 crew members aboard.

The U.S. Coast Guard and Sail4th 250 had not publicly responded to the organization's account as of Saturday afternoon.

The Clearwater has long used its sails to display environmental and social advocacy messages. The vessel was launched in 1969 after being conceived by folk singer Pete Seeger and fellow activists, who sought to draw attention to industrial pollution in the Hudson River. The nonprofit organization said more than 500,000 people have sailed aboard the vessel since its launch as part of its mission of environmental education, advocacy and preservation.

Sail4th 250 billed the event as the largest maritime and aerial gathering in U.S. history in celebration of the nation's 250th anniversary. The event featured tall ships, naval vessels and aircraft from dozens of countries.

The International Parade of Sail included 48 tall ships from 20 nations traveling a 16-mile route from near Sandy Hook to the George Washington Bridge, passing the Statue of Liberty along the way. The event was broadcast nationally by NBC.