Part of a Lawrence home collapsed in a blaze Tuesday as several fire departments battled for more than two hours to put it out, a Nassau County fire official said.

Flames erupted about 12:45 p.m. at a large, two-story residence on Ocean Avenue and were widespread when the first firefighters arrived, said Michael Uttaro, Nassau County assistant chief fire marshal.

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At one point, portions of the roof, interior floor and ceiling began collapsing, and firefighters were ordered to evacuate, he said. Several tower ladders were used to spray water on the fire, he said.

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Investigators believe an electrical malfunction caused the blaze, but the structural collapse left them unable to access the area where the fire likely started, Uttaro said.

A brother and sister live at the home, but they went out on an errand and came back to the fire, Uttaro said. No injuries were reported, he said.