Hawaiian Electric is pushing back against a lawsuit filed by Maui County last week blaming the utility for triggering the wildfires that have killed more than 100 people, caused billions of dollars in damages and left hundreds missing.

The utility said power lines toppled by high winds likely caused the morning brush fire in Lahaina but electricity had been off for hours when a second fire occurred that afternoon.

Hawaiian Electric’s stock soared more than 40% on Monday.

“We were surprised and disappointed that the County of Maui rushed to court even before completing its own investigation,” Hawaiian Electric CEO Shelee Kimura said in a statement Sunday. “We believe the complaint is factually and legally irresponsible.”

“Unfortunately, the county’s lawsuit may leave us no choice in the legal system but to show its responsibility for what happened that day,” Kimura said.

Hawaiian Electric said power lines appear to have caused the brush fire that started at 6:30 a.m. local time at the intersection of Lahainaluna Road and Hookahua Street in the historic town. The small fire near the downed poles spread into a field near Lahaina Intermediate School.

The Maui County Fire Department responded to the morning fire and declared it had been extinguished, according to the company’s account of events leading up to the wildfires.

Hawaiian Electric crews repairing the downed poles later saw a fire around 3 p.m. about 75 yards away in the field near Lahaina Intermediate School and immediately reported it to authorities, according to the company.

Hawaiian Electric said the power had been off for hours when the crew witnessed that second fire in the field. By the time the county fire department responded to the afternoon fire, they were unable to contain the blaze as it spread out of control toward Lahaina, according to the company.

Hawaiian Electric is facing a dozen lawsuits seeking damages over its alleged role in the fires. Ratings agency Fitch has downgraded the company’s credit to junk, warning that more than $3.8 billion in potential liability poses an existential threat to the company.

The cause of the Maui wildfire outbreak, the deadliest in the U.S. in more than a century, is still under investigation by state, local and federal officials. The Bureau of Alcohol, Tobacco, Firearms and Explosives has dispatched a team with an electrical engineer to help with the investigation.

Hawaiian Electric has informed the ATF that it has records to demonstrate that no electricity was flowing through its wires when the second fire broke out, according to the company.