Bad news for property insurers has been announced by the Insurance Services Office Inc.'s property claim services unit: Its original estimate of insured property losses has surged by $500 million for September's Hurricane Floyd.

The insurance tab for Floyd victims is now estimated at $1.8 billion. The property unit's original figure for the four-day storm was $1.3 billion.

Flood-stricken North Carolina comprised the bulk of the increases, the ISO said. The slow recession of floodwaters prevented a comprehensive appraisal from being made earlier, and the property claims unit found a 4.5 per cent increase in claims filed by homeowners and businesses when it resurveyed insurers. The state's insured property damage now weighs in at $1.25 billion, not including loss-adjustment expenses.

Pennsylvania's reckoned figure also rose to $63 million, and New Jersey's losses are now appraised at $95 million. The new totals for South Carolina are $60 million, Maryland $45 million and Georgia $15 million.

The storm, which was less severe than anticipated but brought heavy rains and flooding, struck sixteen states during the period of September 14 to 17.