NEW YORK--Insurers that represent about $1 billion in coverage for the World Trade Center's property program are bound by a policy form that treats the destruction of the twin towers as one event, a New York jury has found.

However, the federal court jury remained deadlocked on whether the insurer with the largest share of the $3.55 billion program, Swiss Reinsurance Co., is bound by that form.

The jury found that several insurers on the program--including Lloyd's of London syndicates, an American International Group Inc. unit, a Chubb Corp. unit and Employers Insurance of Wausau--all were bound by the so-called Wilprop form, which courts have ruled treats the loss as one event. Those insurers represent $1.06 billion in coverage for the program.

The jury also found that three other insurers--which collectively represent $176.5 million in coverage--were not bound by Wilprop. Jurors were asked to decide only whether the insurers were bound by Wilprop; they were not required to determine which form applied in the absence of Wilprop. The three insurers that the jury said were not bound by Wilprop are Zurich American Insurance Co., Twin City Fire Insurance Co. and a unit of Royal & SunAlliance Insurance Group P.L.C.

While the jury reached a decision on most of the insurers in the litigation, Judge Michael Mukasey sent the jurors back for further deliberations regarding Swiss Re, which represents $878 million of the program's limit. No reason was given for the deadlock.

The jury failed to reach a verdict on Swiss Re Thursday and will resume deliberations Monday.

Swiss Re America Chief Executive Officer Jaques Dubois and a lawyer for WTC leaseholder Silverstein Properties Inc. had no comment on the jury's decision.

The 10-week trial is the first phase in litigation over coverage for the WTC's Sept. 11, 2001, destruction and whether the loss should be treated as one event or two for coverage purposes.

Insurers on the risk have maintained that they bound coverage on the Wilprop form, but Silverstein has contended that at the time of the loss, the program was being transferred to a Travelers Property Casualty Corp. form. Silverstein holds that the Travelers form would treat the loss as two events, entitling the real estate firm to a two-limit payout.