LOS ANGELES — Local, state and federal law enforcement agents swarmed a Burbank home Monday in a training exercise aimed at finding a potential radiological device.

The drill started with the mock detonation of an improvised explosive device in Indianapolis, prompting an FBI investigation, the agency's spokeswoman, Laura Eimiller, said.

FBI agents generated fictional investigative leads in Los Angeles and Burbank, she said, which led them to a Burbank home on the 300 block of West Lutge Avenue.

"The resident suspected his renters of having some involvement with radioactive material that might be located in his home," she said.

Teams comprising multiple law enforcement agencies arrived at the home and detected radioactive material coming from the home's swimming pool, where they found the fake device, Eimiller said.

Monday's mock scenario was part of a three-day exercise that tested local, state and federal response capabilities during a terrorist attack.

Mock explosive devices were also dropped off at seven other locations, including Westfield Topanga Mall, the Burbank Fire Department, other Los Angeles-area homes and a state park, Eimiller said.

Agencies also initiated a mock investigation Tuesday into a possible improvised nuclear device at the Los Angeles Coliseum, said Steven Martinez, assistant director in charge of the FBI's Los Angeles office.

"Intelligence has suggested that terrorist organizations aspire to attack us, here in the United States, with a [weapon of mass destruction] whether chemical, biological, radiological or nuclear," he said at a news conference Tuesday at the Coliseum.

While he acknowledged that the FBI was not aware of any imminent attacks against the United States, he said local, state and federal agencies had to be prepared.

The FBI maintains a "render safe" plan with other agencies that takes effect when an improvised nuclear device has been detected, Martinez said.

In the event of a terrorist attack, local police, sheriff's deputies and firefighters will likely be the first- responders, officials said.

Local agencies have been trained to detect and isolate improvised explosive devices, Martinez added.

A planned attack might play out like a big Hollywood action film in which the villain carries out a plan to destroy everything in the explosive's path, Los Angeles Mayor Antonio Villaraigosa said.

"But while our federal government works day and night to secure our country from such a devastating attack, this scenario can become a reality in an blink of an eye," he said.