At approx. 11:54pm Vallejo Fire units were dispatched to a reported structure fire on San Joaquin Drive in Vallejo Mobile Estates. First arriving units found a fully involved mobile home with immediate exposures threatened on both sides. Crews performed a defensive attack, protecting the adjacent structures and knocking down the fire from the outside. Crews were faced with difficult access issues and heavy fire. VFD personnel were able to save both neighboring structures from significant damage and they remain inhabitable. The involved structure is a total loss and currently under investigation. Both occupants were able to escape unharmed prior to arrival of fire units. One patient was treated at the scene by Medic and released.