Terror probe: Why is threat level still yellow? |

The investigation into a potential Al Qaeda plot in the US has triggered a raft of warnings from federal authorities about suspicious activity around stadiums, hotels, and train stations, among other places. But it hasn’t moved the color-coded terror alert system.

The Department of Homeland Security’s national threat level was yellow – or elevated – before and after counterterrorism agents nabbed Najibullah Zazi. He’s the Denver airport shuttle driver at the center the investigation into an alleged plot that authorities say involves plans to build peroxide-based bombs.

There’s no reason this latest terror investigation should have raised the terror alert, says James Carafano, a homeland-security expert at the Heritage Foundation in Washington.

“What is widely perceived as a system to update the American people about terrorist threats is not really designed for that,” he says. “When you raise the color-coded system, it’s a blunt instrument” that triggers specific actions by law enforcement and federal agencies.

For instance, if the system moves from yellow to orange, DHS recommends that federal agencies restrict various facilities and possibly cancel events. With this latest plot, says Mr. Carafano, not enough was known to merit that sort of precaution. Instead, he says, the advisories that federal agents sent local police were enough to ensure extra vigilance among law enforcement and the public. “This whole incident demonstrates how little utility it has as a terrorist alert system,” he says.