Liability for leak causing mold in condo beneath mine?

[Jeff Wirth]

Bought our first rental property late last year- a vacant, second floor 2 BR, bank owned condominium.  Needed remodeling, i.e. some carpeting, painting, kitchen appliances, countertops, but overall not in bad condition.  The A/C, furnace, majority of flooring etc all in good condition.  Found a good tenant who moved in March 1.  

Got a call last week that the tenant in the first floor unit directly beneath ours was at her door complaining her A/C was leaking water down into their unit.  I visited and sure enough it was...the condensation pipe was clogged and the water was overflowing and leaking through the ceiling in the back closet directly above where our furnace is located(and theirs is as well).  Just got a bill from the owner of the property for close to $3K for mold remediation.  There was some mold I noticed when I visited and looked at their unit where the leak was coming in- I fully expected to get a bill for drywall repair, maybe a section of wet carpet, some painting, etc., but not complete mold remediation.  Does this sound right?  The property is in N.J. and our tenant only started running the A/C maybe a month or so ago.  Any thoughts or suggestions would be welcome- I guess I will just turn the bill over to my insurance company if this is my responsibility.