052099 @1815 hours : Box 428, 9th & Elm streets was transmitted for a reported "garage" fire in the 300 block of Moss street. E1,3,9, L3, Sn1, R1, chiefs 3 & 6 responded. Companies gave "smoke showing" enroute and arrived to find a 2&1/2 story vacant EOR dwelling with fire on all floors at 317 Moss street.. The fire was spreading to exposures 2 (a similar attached dwelling) and 3 (a rear garage). Fire venting out the front of the building also involved a telephone pole & 4800 volt transformer. With all companied commited and the fire spreading, a 2nd alarm was transmitted at 1826 bringing E13,5, L1, & C 1, & 2. Companies brought the fire under control in 1 hour using numerous 1&3/4 inch handlines. The attic dormer of the main fire building collpased during the blaze, which caused moderate damage to the 2 exposure buildings. The cause of the fire is believed to be arson-police had 2 suspects in custody by the time the fire was under control. 317 Moss street suffered a suspicious fire 1 week ago.