Janesville police were called to a multi-family home in the 600 block of South High Street about 2:30 a.m. Tuesday for a report of a burglary in process.  Officers arrived to find the suspects had already fled, but a fire was burning on the second floor.  The downstairs tenants had already escaped.  Police helped the upstairs tenants evacuate and used fire extinguishers until the fire department arrived.  One officer was treated for fire inhalation.  Police suspect the fire was started by the burglars.