Hundreds of New York City landlords whose apartment buildings remain without heat or power after Sandy are being warned to get repairs lined up promptly as cold weather looms.

Under estimates Mayor Bloomberg gave Monday, more than 800 storm-damaged apartment buildings lack heat because equipment in the buildings needs repair. Roughly 500 lack power. The vast majority are relatively small buildings, under six stories.

A city program called NYC Rapid Repairs provides free fixes to get heat, lights and hot water back on after the storm.

Bloomberg says landlords who don't sign up or arrange their own repairs quickly could face fines under city law.

An estimated 6,000 private homes also lack heat and power. But it's unclear how many of those are rented and subject to landlord laws.