The experts come from both the government and the private sector and are concerned about the vulnerability of chemical plants across the country.
Republican Senator Susan Collins of Maine chairs the Senate committee that reviews U.S. homeland security efforts.
"To us, those facilities are vital parts of our economy that create jobs and improve our lives,? she said. ?To our enemies, they are weapons waiting to be used against an unsuspecting population."
The Environmental Protection Agency (EPA) says there are 123 chemical plants in 24 states where a release of dangerous chemicals could threaten more than one million people.
Richard Falkenrath is a security expert with the Brookings Institution in Washington. He contends that relatively little has been done since the 2001 terrorist attacks to safeguard chemical facilities from terrorist attack.
"The chemicals that we are talking about today are in many cases identical to those used on the battlefields of WWI,? he noted. ?They are enormously dangerous. They are produced in truly massive quantities, shipped and stored in many cases next to very dense urban populations and present, in my opinion, the single greatest danger of a potential terrorist attack in our country today."
Some members of Congress from both major political parties are now pushing to enact new federal laws that would tighten security at chemical plants, especially those located in large population areas.
The Department of Homeland Security is devising a plan, but some lawmakers say it is not being done with the urgency that is required.
Senator John Corzine, a Democrat from New Jersey, comes from a state where 11 major chemical plants are located.
"This is an issue where I think lives are at stake,? he said. ?We would not tolerate this kind of site security oversight at our nuclear power plants. The public knows that."
In addition to the security concerns, experts urged the government to do much more to prepare for the aftermath of a potential terrorist attack on a chemical plant.
Carolyn Merritt chairs the government board that investigates accidents at chemical plants around the country.
"Many incidents that the Chemical Safety Board has investigated reveal serious gaps in how well companies, emergency responders, government authorities and the public are prepared for a major chemical release. These gaps in preparedness leave Americans vulnerable," she added.
Experts and lawmakers generally agreed that some form of federal legislation is needed to require chemical plants to strengthen their security. At the current time, that responsibility is largely left to the companies themselves.
A federally-funded report last year found that nearly 75 percent of the chemical plants surveyed had taken some steps to improve security since the 2001 terrorist attacks. But the report also found that less than half of the facilities had done much to improve communications or emergency training in preparation for a possible attack.