The Lincoln Memorial in Washington, D.C. was closed briefly Monday after authorities discovered several suspicious items.

The items were found to pose no threat and the memorial was re-opened several hours later.

Authorities said they included a bottle filled with an unidentified liquid and two messages, with references to anthrax and bombs.

The incident appears to be the type of hoax that has gained increasing attention since the 2001 terrorist attacks in the United States and anthrax-laced letters that killed several Americans in 2002.

Some information for this report was provided by AP and Reuters.