One person is believed to be dead after part of a train derailed Thursday morning in Sanford, Florida, CNN affiliate WKMG reported, citing authorities.

The train derailed near a yard where trains are maintained around 6:45 a.m., WKMG reported. Aerial video showed four open-top freight cars lying on their sides just off the track, with other cars still upright.

Workers were searching for the presumed victim, WKMG reported. The overturned cars spilled what appeared to be gravel that they were carrying, and workers were using excavators to dig around and remove gravel beside one of the cars, the video showed.

Details about how the derailment happened weren't immediately available.