Anaheim police said the item turned out to be a rolled-up piece of paper with some kind of message.
Sgt. Bob Dunn said a Disney Resorts guard reported seeing the object around 7 a.m. near the ticket booths during the morning walk-through. The guard didn't know what the object was, and a bomb squad was called in. The entrance area between Downtown Disney and the gates to California Adventure and Disneyland was shut down during the investigation, and people were not allowed to leave or enter the park.
After the object was deemed harmless, officials reopened the park at about 11 a.m.
Dunn said the man who placed the object in the tree came forward and apologized. Dunn described the message on the paper as "spiritual," but did not specify the exact content.
Police said charges are possible pending the outcome of an investigation.
Meantime, a Disney Resort official said the park will extend its hours Saturday as a thank-you to the guests who were affected by the morning's events. Disneyland will close at 1 a.m. and Disney California Adventure will close at 10 p.m. The park also added an additional "World of Color" show at California Adventure at 10:15 p.m. as well as a "Fantasmic!" show at Disneyland at 11 p.m.