WASHINGTON -- The U.S. Department of Transportation (DOT) is advising shippers and transporters of hazardous materials to consider altering their routes to avoid populated areas "whenever practicable," and to take other safety precautions as a result of a heightened state of alert related to the threat of additional terrorist actions in the United States.

U.S. Transportation Secretary Norman Mineta urged transportation workers to "watch for and report any suspicious activities they may see." Hazardous materials vehicles should not be left unattended, and "companies should ensure that hazardous materials are in responsible and reliable hands," he said.

Maneta also said hazardous materials carriers would be "under close observation from both state and local officials for improper placarding and for trucks that are traveling along unusual or unexpected routes." State and local authorities have been advised to take control of vehicles "off normal routes," he said.

Meanwhile, the FBI has asked the National Association of Chemical Distributors (NACD) to urge its members to increase security measures and be alert for "suspicious persons and customer orders." The bureau said companies should contact local FBI offices if concerns about such cases arise.

The NACD issued a series of suggestions to its member companies regarding security measures, including advice to maintain high levels of security at facilities, being careful in admitting visitors to facilities, monitoring deliveries of materials to facilities, contacting local emergency officials to advise them of security efforts and determine any assistance they may need, and being prepared to handle inquiries from the media and the public regarding your operations.

The complete NACD advisory is available on the association's Web site at www.nacd.com.