The main event of TOPOFF 2 has Seattle police and firefighters, along with health experts, county, state and federal officials responding to a simulated radiological dispersal device in south Seattle. The "dirty bomb" exercise began Monday and will run continuously for 36 hours.

The FBI and the Department of Homeland Security/Federal Emergency Management Agency are directing federal participation and oversight of the exercise. Visible, full-scale play ends on May 14th. A scaled down, table-top exercise will continue through the end of the week but there will be no public interaction.

Most exercise activity will be on a vacant lot in the 2900 block of Airport Way South, across from the Tully's Coffee roasting plant. To facilitate exercise activity, Seattle Police will close the southbound curb lane of Airport Way South from South Walker to South Spokane Street from 8 a.m. Monday, May 12 until 8 a.m. Wednesday, May 14. Businesses in the area will remain open as usual.