HOUSTON (AP) — Victims of a deadly explosion at a BP PLC refinery have settled all but one of the more than 4,000 lawsuits that were filed in state court after the blast, attorneys said Friday.

The victims' attorneys announced that four lawsuits have been settled over the March 2005 explosion that killed 15 people and injured more than 170.

State District Judge Susan Criss said a hearing is scheduled next month in the only remaining case in state court. One lawsuit is pending in federal court, and attorneys plan to appeal another suit that was dismissed in state court.

As has been the case when other blast-related suits, the terms of the settlements announced Friday were confidential.

A spokeswoman for London-based BP did not immediately return a call Friday.

The explosion occurred after a blowdown drum overfilled with highly flammable liquid hydrocarbons. They ignited at the startup of the isomerization unit — a device that boosts the octane in gasoline. Alarms and gauges that were supposed to warn of the overfilled equipment did not work properly.