The daughter and a grandson of Kathleen Kennedy Townsend, the eldest daughter of Robert F Kennedy, are believed to have died after a canoe they were using in the Chesapeake Bay did not return to shore.

The missing relatives were identified as Maeve Kennedy Townsend McKean, 40, and McKean's eight-year-old son, Gideon Joseph Kennedy McKean.

In a statement, Kathleen Kennedy Townsend said that with profound sadness, I share the news that the search for my beloved daughter Maeve and grandson Gideon has turned from rescue to recovery.

Kennedy Townsend, who served two terms as Maryland's lieutenant governor, is the eldest daughter of Robert F Kennedy, former attorney general of the US, who was assassinated in 1968.