Independence Day weekend at Daytona International Speedway got off to a troubling start. Daytona Beach Police responded to a bomb threat at the speedway Thursday afternoon, the Orlando Sentinel reports. Police Chief Craig Capri said authorities investigated the area and found no evidence of explosive devices. An anonymous caller reportedly said multiple devices at Daytona were set to go off in 30 minutes. Once the 30 minutes passed, police spent roughly an hour sweeping the area, according to spokeswoman Lyda Longa. Authorities reportedly obtained a phone number, and are attempting to identify the source of the call. The bomb threat does n... NESN.com