Security tightened at Delaware base used by U.S. vice president

(Reuters) - A Delaware Air National Guard base used by Vice President Joseph Biden boosted its security level on Wednesday after a number of vehicles approached the gates, raising suspicion, a base spokesman said. Five vehicles stopped at the New Castle Air National Guard Base gates near Wilmington, ostensibly to ask for directions, on Monday and Tuesday, said Lieutenant Colonel Len Gratteri. It was not uncommon for drivers to ask for directions, he said, but the sudden increase in the number of cars stopping put security officials on the alert. "While we can't discuss specifics of our security measures, our actions are simply a matter of procedure and increased vigilance," Gratteri said. Biden has used the base because it is near his home in Delaware. While no specific threat has been identified, Gratteri said, police and U.S. military officials have been notified and, as a precaution, a heightened threat level has been put into place. A spokesman for the Delaware State Police said patrols were increased around the base and other military facilities in the state. Delaware's biggest base is Dover Air Force Base. The New Castle base is home to the 166th Airlift Wing, a transport unit. (Reporting by John Clarke in Washington)