Cary, N.C. — A day after a ruptured gas main created a fireball that burned out of control for six hours, closing a major intersection and forcing the evacuation of nearby businesses, officials were trying to determine how a contractor could have drilled into the gas line.

A crew from Fulcher Electric Co., a contractor hired by Cary to install new traffic signals at the intersection of Kildaire Farm Road and Tryon Road, hit an 8-inch steel gas line Wednesday morning. The crew's truck somehow ignited the gas, which erupted into flames that shot 100 feet into the sky, officials said.

Traffic was diverted around the intersection, and some nearby stores and businesses were closed as a safety precaution. No injuries were reported.

Crews with PSNC Energy capped off the damaged line at about 5 p.m. Wednesday, and the fire burned itself out a short time later. Road crews worked overnight to repair the asphalt, which had buckled from the fire's intense heat, and the intersection reopened to traffic Thursday morning.

The incident was the second time in less than a day that a gas line had been punctured by crews working on projects related to the widening of Tryon Road. A Tuesday afternoon rupture at Cary Parkway was capped off quickly without problem.

Cary town engineers met Thursday with officials from Fulcher Electric and from utilities to determine the cause of the incidents.

"We don't know what went wrong," said Joe Moore, a senior engineer with the Cary Engineering Department.

No estimate of the cost for battling the fire and repairing the damage to the gas main and the road had been compiled Thursday. It also was unclear who will be responsible for picking up the tab.

"We will start investigating what occurred. Who was where when? What happened?" said Nicole Hussey, a risk management specialist for Cary. "Once the investigation is completed, then that determination (of who pays) will be made."

The contractor obtained the proper paperwork from Cary to ask utilities to mark their underground lines before drilling took place, Moore said. It was unclear, however, whether the lines were ever marked or if the Fulcher Electric crew missed marks if they were in place.

The fire and the repair work would have eradicated any evidence that the underground lines had been marked. Crews dug up and replaced 8 inches of asphalt over a 100-foot-long section.

"What makes it a little bit more difficult in this case is, with the amount of damage out there, it is going to be hard to trace what marks were (there)," Moore said.

Fulcher Electric said it would dedicate one person on its work crews to making sure paperwork and pavement markings were clear before work started. The company also will dig holes by hand to ensure no utility lines are struck, officials said.

Meanwhile, PSNC officials said they would move gas lines that likely would be in the way of planned construction along Tryon Road. Lines will be moved from two locations near the intersection of Summerwinds Drive and Tryon Road and at Frostwood Drive and Autumn Circle, officials said.

"(We told them to) focus on those three areas to either remove the gas line or relocate it by moving it outside the construction zone or burying it well deep of the excavation area," Moore said.