At 17:59 the box assignment for a reported residential structure fire put the Dagsboro, Millsboro & SCEMS Medic 103 on the street. Medic 103 arrived with in 1 min to find a mobile home w/ heavy fire venting from the C/D corner & a vehicle in the driveway. E731 under Chief Glenn marked on the air with a crew of (5) five & advised of Medic 103's report. E731 arrived to find as reported & stretched to the front door for fire attack. Both E831 & Engine/Tanker 73 arrived simultaniosly w/ E831 assuming the 2nd due engine hitting the hydrant & securing E731's water. The crew from E831 pulled the back up line while the Engine/Tanker's crew opened up & conducted a primary search. Rescue Co. 73 & 83 both arrived & began to set up lighting & assist with opening up, however Rescue 83 was soon diverted to a MVC w/ reported rescue in Millsboro. The fire was quickly knocked & the primary search yielded only the family pet, a 1 yr old black lab (priority 4). After an extensive overhaul crews began picking up. Crews operated for approx. 2hrs before returning to service.