Workers drilling underground pathways — possibly to carry new fiber-optic cables — struck buried natural-gas lines twice in three days at the senior living community in Aurora that was rocked by a fatal explosion last week.

The second of those leaks, which was reported Friday afternoon, could be the cause of the blast that killed 82-year-old resident Carol Ross and burned several homes at the Heather Gardens complex.

“We were (already) there when the explosion and fire happened because we were investigating a gas leak,” Aurora Fire Rescue spokeswoman Sherri-Jo Stowell said on Monday.

Xcel Energy spokesman Mark Stutz confirmed both gas leaks were caused by the same company, which he declined to identify, and both involved horizontal directional drilling, which allows workers to burrow underground without digging open trenches.

“Their equipment ran into our line,” Stutz said of the two gas leaks at Heather Gardens.

Leslie Oliver, a spokeswoman for Comcast Colorado, confirmed Monday that its contractor ICS Communications has been working on the company’s Xfinity fiber-optic project at Heather Gardens. But she did not acknowledge whether that work was connected to the gas leaks.

ICS Communications did not respond to an inquiry from The Denver Post on Monday.

The Post has filed a public-records request with the city of Aurora to determine whether any other companies had active work orders at Heather Gardens.

The leak on Wednesday was repaired that day, according to Xcel, but the company’s employees weren’t able to repair Friday’s leak despite reaching the property within 30 minutes of the first call.

“Upon arrival, we were working with the local fire department to secure the area and were in the process of addressing the leak when the explosion occurred,” Xcel said in a news release.

Stutz also declined to release the number of calls Xcel received about potential gas leaks at Heather Gardens since the project started, citing Aurora Fire’s ongoing investigation.

Stowell said the investigation into whether the leak caused the explosion could take weeks. But Heather Gardens, at the request of the Colorado Public Utilities Commission, suspended all underground construction projects until further notice.

Heather Gardens advertises itself as an age-restricted community of about 4,500 people located southeast of Interstate 225. There’s a golf course, community center and an assortment of classes run by its residents. Ross was well-known for her knitting and crochet classes.

This summer, Heather Gardens’ homeowners association notified its residents that Xfinity, which is owned by Comcast, would be installing fiber-optic cables underneath the community. These kinds of cables provide a faster, more reliable way to make phone calls and surf the internet.

“There will be large machinery that will be present,” according to a memo from Xfinity posted to the HOA’s website. “Please be advised that some areas will be fenced off and require only authorized construction teams.”

The way fiber-optic cables are often laid is through a process called horizontal directional drilling. It’s a trenchless technology, which means workers use special tools to burrow underground tunnels for new cables, pipes or conduits, according to the Occupational Safety and Health Administration. It’s used a lot in urban areas where it’s not practical to dig trenches, but it comes with increased risks because workers can’t see other, buried utility lines.

Investigators are going to have to figure out whether Comcast or its contractor called 811, the number for Colorado’s utility locator service. Calls to the 811 line aren’t public records, officials said, but any person or company digging on a piece of property is supposed to have the utility lines marked before starting. OSHA says it’s especially important for projects that involve directional drilling because it’s the only way to know where gas, electric and other utility lines run.

“Striking underground natural gas lines may present explosion and fire hazards in the workplace and surrounding areas … ,” according to OSHA’s website. “Natural gas is easily ignited by an open flame, static electricity, glow plugs from diesel engines, or sparks from the HDD machine or nearby equipment.”

Similar accidents caused explosions in Nebraska, Wisconsin and Missouri. In each of these cases, a contractor or subcontractor cut a gas line while drilling lines for fiber-optic cables on behalf of a major telecommunications company like Comcast or Verizon.

If the gas lines were properly marked in advance at Heather Gardens, Aurora Fire will then have to determine whether the markings were accurate and/or whether they were ignored.

“It’s going to be a lengthy investigation,” Stowell said.