At Decision Sciences International Corp.'s headquarters, a 20-foot shipping container sits beneath a carwash-size scanner. After about a minute, images of the container's contents pop up on a nearby TV screen, color-coded based on how they interact with naturally occurring subatomic particles.

It's not a pretty picture. There's ammunition, firearms, TNT, alcohol and currency inside. If shielded nuclear material were in the container, the California company's technology would identify that, too, said Chief Executive Dwight Johnson.

"If you're [a customs] officer and you had a manifest that said it's all furniture, you'd stop right now," Johnson said. "It's not all furniture."

Last month, Decision Sciences said it received a contract with the Singapore Ministry of Home Affairs to install one of its next-generation cargo scanning systems at the country's main port. Though a pilot project, Decision Sciences is betting it will lead to further deployments of its technology, which is licensed from the Los Alamos National Laboratory and has been refined for more than a decade.

"In terms of total volume, Singapore is the second largest port in the world," Johnson said. "So this is a very important event for Decision Sciences."

The 70-employee company is one of a handful of firms working on new technology to better scan cargo containers, which became a priority after the Sept. 11, 2001, terrorist attacks.

"The way to look at the next-generation systems is going from human inspection of a projected image to materials identification," said Robert Ledoux, chief executive of Massachusetts-based Passport Systems, which recently deployed a next-generation scanning system in Boston.

Passport System uses high-energy X-rays to identify guns and other contraband based on their atomic number — a measure of their density.

Decision Sciences' scanning technique is passive. It doesn't use X-ray beams to create three-dimensional images or identify what's in a container. Instead, it tracks naturally occurring subatomic particles called muons, as well as electrons, to call out a container's contents.