Update (11:40 a.m. EST): Jeff Smith, a member of Occupy Wall Street's media team, tweets that the fire department has given the all clear after a false alarm: "FDNY says it was just a false alarm about a suspicious pckg. Locals say it's pretty common." 

Original: Tuesday's excitement at Zuccotti Park was supposed to come in the afternoon, with David Crosby and Graham Nash scheduled to play a concert, but they may not make it into the park as police and firefighters have reportedly barricaded the area after a bomb scare.

The bomb squad is en route to the park to investigate a suspicious package, which was reported at 10:33 a.m., New York police and fire officials said via telephone. Twitter is starting to light up with reports of barricades: "Appears NYPD has barricaded Zuccotti park OWS. Some said due to a suspicious package," tweeted David Zomb. Longtime City Hall reporter Harry Siegel also tweeted, "Three sides of Zuccotti barricaded in last hour I'm told, apparently b/c of gas leak-but feels like a pen, OWS concerned about NYPD moving in." Others on Twitter reported arrests in progress and riot police massing nearby. Emergency officials haven't confirmed that.

We'll keep you abreast as things develop, but you can also follow along on the encampment's live stream, which is currently showing barricades around at least part of the park: