Enstar Natural Gas needed more than 11 hours to shut off a leaking gas line that caused two explosions and fires in a Kenai neighborhood, as the company responded to damage caused by the 7.1-magnitude earthquake that struck Southcentral Alaska in January, according to an incident report Enstar filed with pipeline regulators on Wednesday.

The report also said the property damage to homes and Enstar's own expenses totaled more than $675,000.

The company said the leak occurred when a 1.25-inch main line separated at a weld joint, causing an "unintentional release of gas" apparently related to "natural force damage" as the earth rattled during the quake centered about 162 miles southwest of Anchorage.

The leak was not caused by a weld failure or equipment problem, the report said.

Gas flow was not shut off until 2 p.m., more than 11 hours after Enstar received a call following the first explosion and more than 12 hours after the 1:30 a.m. earthquake, according to the report.

The unique nature of the leak complicated the response time, said Lindsay Hobson, Enstar's communications manager.

When the company responds to leaks it typically knows where the leak is located because the damage is caused by a contractor or excavator and the line is already accessible.

"Here, several factors lead to a longer shut-off time," Hobson said. Crews had to locate the leak from above ground and they had to wait for owners of cables and other pipes to locate their lines. Also, digging through the frozen soil took extra time.

The report was filed with the Pipeline and Hazardous Materials Safety Administration on Wednesday, standard procedure following such an incident, Hobson said. Enstar also provided an informational filing to the Regulatory Commission of Alaska.

PHMSA officials could not be reached for comment on Thursday.

The leak did not cause any injuries, but led to the explosions and four homes burned, the report said. The Kenai Fire Department, in information it released early this month following its investigation, said one of the blasts shot a roof more than 40 feet into the air. The department also blamed the earthquake for the gas leak.

Enstar's report said the steel main line, buried and running along Lilac Lane, was installed in 1969. The leak did not occur at a service line that receives gas from a main line and extends to houses.

Following new federal regulations, Enstar since 2010 has fitted service lines with excess flow valves, or EFVs, that are designed to stop a leak if a service line is damaged. Enstar adds that equipment to service lines installed before 2010, if it does work on one of those lines.

But the valves are not designed for main lines, and are not required to be installed on main lines, Hobson said.

"EFVs are not applicable to main lines," Hobson said.

As a result, the main line where the damage occurred had no valve to automatically stop the leak.

"Crews shut down the main on Lilac Lane by stopping gas flow to the three tie-in points that fed the street," the report said.

The Enstar report says the company received a call about an "ignition and fire" at 1213 Lilac Lane, almost an hour after the 1:30 a.m. earthquake. The first Enstar employee was on scene about 13 minutes after the call. The Kenai Fire Department extinguished that small fire.

"Over the course of the next three hours, crews worked with emergency responders to evacuate the street, shut down electricity to structures on the street, and locate the gas leak," the report said.

"Crews determined that there was an underground gas leak in front of 1213 Lilac Lane," the report said.

At about 4 a.m., Enstar crews began excavating at the suspected site of the gas leak, digging through up to 4 feet of frost to reach the 8-foot deep main. At almost 6 a.m., a "secondary ignition" occurred at another house, causing a fire that burned four homes. That's the blast that shot the roof off a house, according to the fire department.

"Crews repaired the broken main and restored service to non-affected homes at (about 6 p.m.)," the report said.

Enstar estimated its costs at $125,000 for damage, repairs and response, including more than two weeks searching for and removing hidden pockets of gas that had escaped and remained trapped in the earth.

During the leak, 406,000 cubic feet of gas escaped, a loss Enstar valued at $2,749.

Enstar estimated the damage to the homes at $550,000. Some homeowners said shortly after the fires that they were working with insurance companies to receive compensation.

Hobson said Enstar isn't responsible for the damages to the houses, because the leak was caused by an earthquake.

"There's no obligation to pay that, because it's a force majeure," Hobson said, an unavoidable accident.