SAN DIEGO (CBS 8/CNS) - The FBI is investigating a pair of hoax bomb threats that targeted Southwest flights flying out of Lindbergh Field.

Tuesday's local threat was made against Flight 682, which was scheduled to head from San Diego to Dallas around 7 a.m., according to San Diego Harbor police.

Though the flight was delayed by an hour Tuesday morning, passengers had yet to board the plane when the threat investigation began and no evacuations were necessary.

The threat, made via Twitter, was one of several made against various Southwest flights over the last several days, including an earlier one made against another flight out of San Diego headed to Dallas on Monday.

"The safety of air travelers is our top priority," a police statement said. "The Airport Authority will work closely with the proper authorities as the investigation into this matter is conducted."

A string of bogus online threats have targeted planes from coast-to-coast over the past few days.