U.S. cities on guard for potential terror threats

While millions of Americans celebrate the country's independence, law enforcement  officials will keep a look out for potential threats.

There are no specific plots that have been uncovered, intelligence sources tell ABC news that people will likely see a stronger security presence this year.

"There's always a concern during national holidays in the United states for the following reasons. It's symbolic to extremists groups," Matt Kozar, a security analyst, said. "To launch an attack and in particular to be successful on that date would be a big deal for them."

Authorities are concerned about lone wolves looking to wreak havoc during an important American holiday.