Burns added deputies are aware of that.
"We are not asleep," he said. "We are being diligent."
California Highway Patrol officials said they have remained vigilant since terrorists flew planes into the World Trade Center and U.S. Pentagon on Sept. 11.
"Everyone has to have their eyes and ears open for anything out of the ordinary," said local Highway Patrol Capt. Teresa Sumprer.
She added while the Imperial Valley is not a high-profile area, it is difficult to say where terrorists might strike and because of that authorities must remain aware of the threat.
She agreed with Burns that while the Valley might not be the focus of an attack, the area could serve as a corridor because of the international border and Interstate 8.
At the ports of entry, the U.S. Immigration and Naturalization Service and U.S. Customs Service have remained in the highest state of alert since the terrorist attacks.
Lauren Mack, an INS spokeswoman in San Diego, said that alert has never wavered. She said the FBI warning does not change the status at the ports.
She added if there was more specific information such as whether terrorists were going to target ports or try to cross through a port of entry, that might cause federal authorities to reconsider where they place their resources.
Mack added the high state of alert will remain in place and there has been no end date set for the alert status.
Other state law enforcement agencies and the authority in charge of key Southern California's airports have reacted to the latest FBI terrorist alert with assurances they have not let down their guard.
‘‘Ever since the Sept. 11 terrorist attacks, our officers have been on high alert and we continue to remain so. No specific location or time was given for this latest alert, so there's not much more we can do. We're already on the highest alert,'' Officer Jason Lee, a Los Angeles Police Department spokesman, said Monday night.
Earlier Monday, the FBI issued an alert asking law enforcement and the American public to be on the lookout for a Yemeni man and several associates who might be plotting a terrorist attack as early as Tuesday.
‘‘This is a national alert, there has been nothing specified that it will happen in Los Angeles. We're on heightened alert. There have been no specific targets mentioned and no specific areas highlighted,'' said Deputy Ron Bottomley, a Los Angeles County sheriff's spokesman.
Security at the Golden Gate Bridge was increased following Sept. 11, and the heightened alert status continues with the new warning, said Sgt. David Rivera of the Golden Gate Bridge District.
‘‘We're performing our security checks and standard operating procedures,'' he said.
Police in San Jose also were already on high alert.
‘‘We have a number of places in San Jose that we think would be of interest to somebody in this situation we're talking about, so we have the resources in place,'' said Joseph Deras of the San Jose Police Department.
Los Angeles World Airports, the agency in charge of Los Angeles International Airport, Van Nuys Airport and Palmdale Regional Airport in Los Angeles County and Ontario International Airport in San Bernardino County, also reported no significant change to its heightened security status.
‘‘Airport officials are in contact with local, county, state, federal and international agencies and we're on top of worldwide situations. The airport has been on high alert since Sept. 11,'' spokeswoman Gaby Pacheco said.
>> Staff Writer Darren Simon can be reached at 337-4082.
>> The Associated Press contributed information to this story.