At 23:41 the box assignment was transmitted to the DVFD for a house fire at 116 East Clogg Drive, Holiday Acres, bringing the Millsboro FD & SCEMS Medic 103. Engine 731 responded with a crew of (4) four at 23:45 followed closely by Engine 831. Both units were advised it was believed to be a working alarm & there was confirmed (1) one male patient out of the residence. Engine 731 arrived to find a 60x12 mobile home well involved with Asst. Chief Furbush as IC. The crew of Engine 731 (Capt. Blades & FF Glenn) pulled a 1 3/4" smooth bore and prepared to make entry. Engine 831 arrived and pulled a 1 3/4" back up line. As the crew from Engine 731 was making entry, Engine/Tanker 73 arrived dropping a 5" supply line from the entrance of the development for the tanker companies to pick up. By this time the interior crews had the fire knocked & beginning to mop up. IC placed the incident under control at 00:00 hrs, holding all units for mop up & requesting a (1) one engine transfer to the DVFD. Crews were held for the next 2 hrs. for overhaul due to fire extension under the residence. Crews were returned to service at 02:07 hrs. The DSFMO is investigating the cause. The male occupant refused treatment.