Security measures remained normal at the Los Angeles International Airport (LAX) and other airfields on July 25 despite a national terror alert in the U.S.

There were no changes in security measures at major airports despite the national alert detailing terrorism "dress rehearsals" that may have played out in recent months at several U.S. airports, officials said.

The bulletin, not intended for public dissemination but obtained and released on July 24 by the U.S.-based National Broadcasting Corporation warned of "a surge in recent suspicious incidents" involving items found in airline passengers' luggage.

Jennifer Peppin, a spokeswoman for the U.S. Transportation Security Administration (TSA), said the alert resulted in "absolutely no changes" in security measures at any airports.

Peppin described the directive as "very routine," saying one of its general type goes out "nearly every day."

"I think it's really important to drive home the fact that there was no specific or credible threat (disclosed) in the bulletin that went out earlier," she said.

The TSA communique refers to four occurrences, including the July 5 discovery of two duct tape-wrapped cooler packs in a checked bag at San Diego International Airport.

The freezer bags had clay inside of them "rather than the normal blue gel," according to the TSA.

Peppin said she did know offhand of any of the incidents occurring at LAX.

The other suspicious incidents -- which occurred in Baltimore, Houston and Milwaukee over the last 10 months -- involved the seizure of "wires, switches, pipes or tubes, cell-phone components and dense, clay-like substances," the alert states.

The discoveries "may indicate terrorists are conducting pre-attack - 'dry runs' similar to dress rehearsals," the document warns. "Past terrorist attacks and plots show that such testing generally indicates attacks will soon follow, according to a joint FBI and Homeland Security assessment."

Despite the apparent urgency of the memo, however, U.S. federal officials publicly described it as routine.

"There is no intelligence that indicates a specific or credible threat to the homeland," the TSA asserted in a statement posted on its website.

"We need to be clear there is no specific, credible threat related to this information. It's simply part of an overall environment of being alert," Peppin said.