"We are pleased to have resolved substantially all of the claims arising from the explosion," London-based BP said in a statement. "Our goal from the outset has been to fairly compensate people harmed by this tragedy."
The terms of the settlements were confidential.
The blast there killed 15 people and injured more than 170.
The plaintiffs -- Luis Garcia, 26; Esteban Huerta, 57; Charles Pinder, 50; and Olivia Palton, 42 -- were employed by various independent contractors who worked in and around the Texas City refinery located about 40 miles southeast of Houston.
They claimed to have suffered a variety of injuries, including back and knee problems and post traumatic stress disorder.
Brent Coon, an attorney representing Garcia and Huerta, said he has mixed emotions.
"The terms of the settlement provide immediate relief and closure for our clients and avoid the potential for a lengthy appeal," he said. "But for me not to get the final closure, which is having a jury come back and stick it to (BP), is disappointing."
None of the blast-related lawsuits that have gone to trial have been settled by a jury verdict.
The settlements were reached Monday night, nine weeks into the trial in Galveston.
A trial on the remaining lawsuits is scheduled for September, but Coon said he thinks those cases will be settled before then.
The explosion at the plant, about 40 miles southeast of Houston, occurred after a piece of equipment called a blowdown drum overfilled with highly flammable liquid hydrocarbons.
The excess liquid and vapor hydrocarbons then were vented from the drum and 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.
The U.S. Chemical Safety and Hazard Investigation Board found BP fostered bad management at the plant and that cost-cutting moves by BP were factors in the explosion.
Still pending is a decision from a federal judge in Houston on whether she will accept a guilty plea from BP to settle a criminal investigation by the Department of Justice on the explosion.
The much criticized plea deal calls for a $50 million fine and sentences the oil giant to three years' probation for its role in the blast.
Many blast victims think the fine is low and that BP would not meet its safety obligations at the refinery.
Federal prosecutors and BP have defended the plea agreement, saying it's the harshest option available in assessing criminal punishment. A congressional committee is investigating the deal.
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