Authorities with bomb-sniffing dogs have stepped up their random inspections of baggage docks at Logan International Airport in Boston, airport sources say.

It was from Logan that Arab hijackers were able to board the jets that they used to torpedo the World Trader Center towers.

Instead of weekly inspections, agents are now doing daily inspections, sources say, even showing up twice in one day.

The dogs are trained to find explosives in luggage and parcels. In addition to the federal inspections, security companies hired by airlines use X-ray machines, similar to the ones at terminal checkpoints, to scan for bombs in luggage.

Cargo shipped by "unknown" shippers also is run through X-ray machines.

American's machine, however, is known to break down, says an American employee at Logan. American Flight 11 was the first plane to hit the Trade Center.

"We scan if the machine's working," the employee said. "Otherwise, bags and parcels just go down the chute and into the pods" for loading onto planes.

"We have a lot of antiquated equipment in Boston," the American source complained. "And no one wants to fix it because of the money involved."

Global Aviation Security Services Corp. handles security for American.

In another development, FBI agents returned to Logan this week to interrogate an Egyptian-American cargo worker who broke down under questioning, sources say.

The man, who was wearing a T-shirt emblazoned with the American flag, protested that he was a U.S. citizen who loved his country.

The suspected ringleader of the hijackers, Mohamed Atta, is a member of the Egyptian Islamic Jihad. He flew on Flight 11.