A fire that heavily damaged a business complex in York was deliberately set, while the cause of a fire that detroyed a Yarmouth business complex remains under investigation.  That's according to the state Fire Marshal's office.  Fire investigators say the building in York had been burglarized before the fire was set on Saturday night.  Law enforcement officials say they're investigating burglaries at several commercial establishments that might be related to the fires.  They're asking the public to report any suspicious activity at commercial establishments after normal business hours.