A sequel to the blockbuster thriller "The Da Vinci Code" is set to lift the veil on mysterious Freemason symbols carved into the very fabric of the historic streets and buildings of the US capital.

Novelist Dan Brown has set the new adventures of his hero, scholar-adventurer Robert Langdon, right in the heart of Washington, which could reveal some astonishing facts for history buffs.

Brown "had a contact with us but then cut it short. We are all sitting around waiting for his book to come out but nobody knows what he's going to say," Akram Elias, grand master-elect of Washington's Grand Lodge, told AFP.

According to the pre-publicity, the book -- working title "The Solomon Key" -- will feature Langdon hero of the mass-selling "The Da Vinci Code" and who was played by Tom Hanks in the hit film version.

"For the first time, Langdon will find himself embroiled in a mystery on US soil. This new novel explores the hidden history of our nation's capital," Brown wrote in a posting on his official website.

Washington has strong historic roots in Freemasonry -- an old and widespread fraternity which traditionally practised secret rituals.