Lockdown lifted at US naval base in Italy after 'security incident'

LONDON -- A U.S. naval base in Italy was briefly placed on lockdown on Wednesday as officials investigated a possible "vehicle-born incendiary explosive device," which was later determined to be "no threat."

Naval Air Station Sigonella in Sicily said its shelter-in-place order was cleared at about 11:25 a.m., more than 3 hours after it first posted about an "ongoing situation" at an entry control point.

"We are grateful to our Navy Security Force personnel for their quick response," the base said.

The base said in an earlier social media post that a "lockdown/shelter-in-place remains in effect." Traffic into and out of the base had been "secured" at that time, but was later reopened, the base said.

Security forces had been alerted to the possible explosive device at 7:54 a.m. and put a shelter-in-place order out about 40 minutes later, the base said in a press release.

"Navy Security Force personnel responded to the situation immediately to investigate," the press release said, adding, "Italian explosives disposal specialists, in coordination with host nation police, inspected the package and determined it was not a threat."

Signolla supports dozens of U.S. military commands from several branches, including the Navy, Army, Marine Corp and Air Force. NATO commands are also supported by the base.

The air base has been in operation since 1957 and covers some 1,300 acres over four main sites.

ABC News' Joe Simonetti and Zoe Magee contributed to this report.