Aug. 17--The technology exists to detect liquid explosives -- at least three Massachusetts companies have created such tools -- but the federal government says it's still not ready to deploy the devices in the nation's airports.

The Transportation Security Administration, the federal agency in charge of airport security, is testing products from American Science and Engineering Inc. of Billerica; Ahura Corp. of Wilmington; and General Dielectric Inc. of Acton.

AS&E's SmartCheck system uses low-powered X-rays to scan passengers for hidden items like bottles of liquid, while Ahura and General Dielectric use lasers or microwaves respectively, to identify the contents of a sealed bottle. The TSA is also testing seven other devices made by companies in the United States, the United Kingdom, and Japan. But TSA spokeswoman Amy Kudwa says that none are ready to be deployed because of reliability and feasibility issues.

But after this month's foiled terrorist plot to smuggle liquid explosives aboard jumbo jets, the government may not have the luxury to wait. Charles Slepian, founder of the Foreseeable Risk Analysis Center, a transportation security firm in New York, said that technology for detecting explosives in carry-on bags is well understood and readily available, but that the US Department of Homeland Security is reluctant to spend the large sums needed to deploy it at hundreds of airports.

"Now they're embarrassed because they have to say that we have nothing in place," said Slepian. "Shame on us. We've had the science for years."

Since the early 1990s, AS&E has made SmartCheck, a $50,000 low-intensity X-ray scanner that can spot a bottle of organic compounds in a passenger's pocket.

But is the liquid an explosive, or a batch of baby formula? Ahura says its $30,000 handheld laser scanner, the First Defender, can answer the question. The device can "see" through glass or plastic bottles and identify any of 2,500 different chemical compounds in about 15 seconds. The FBI and New York City police already use the Ahura system, which went on sale about a year ago.