From Kentucky to Virginia, the fast-moving June 29 storm created outages at 911 emergency call centers.

But as the FCC pursues the causes and effects of those problems, it was the massive and still-unexplained outages in Northern Virginia that drew specific comments Thursday from FCC commissioners who underscored the importance of 911 during events as expansive as a terrorist attack and as personal as a heart attack.

At an FCC public hearing, commissioner Robert M. McDowell said the storm was “no doubt a trying time,” but it also may have exposed “fundamental weaknesses” in a system of heightened importance for the Capital area, with its risk of attack. “Having hardened and reliable 911 systems is crucial,” he said.

Chairman Julius Genachowski recounted an emergency call for a heart attack victim in Prince William County, where the 911 center lost service. The caller got a busy signal but was able to find a non-emergency line and get the victim help.

“That can’t be the way it works,” Genachowski said.

FCC officials will contact 911 emergency call centers in areas hit hard by the June 29 storm to determine whether problems with incoming calls and information on callers’ locations extended beyond the significant issues already known.

David Turetsky, head of the FCC’s Public Safety and Homeland Security Bureau, outlined the broadening review to the five FCC commissioners at their monthly public meeting. The session did not include statements from phone companies or public safety officials, although FCC staff members have begun contacting them and reviewing outage reports.

The FCC also is seeking public comments as it digs deeper into the 911 breakdowns, which it said apparently were “isolated” in Ohio, Kentucky, Indiana and Pennsylvania but “systemic” in West Virginia and Northern Virginia.

Verizon, the carrier for the Northern Virginia 911 centers that experienced outages, continues to investigate the problems.

A nonworking backup generator at a company site in Arlington contributed to the outages, as did a power loss at a Verizon office in Fairfax, company spokesman Harry Mitchell said.

Verizon and local public safety officials have disagreed about the extent and duration of the 911 failures. Verizon has said outages lasted through June 30 in an area that would include 1.5 million people in Fairfax and Prince William counties and Manassas and Manassas Park.

But local 911 officials said it was July 3 before callers’ phone numbers and addresses reliably showed up in Arlington, parts of Alexandria and other areas of the region. That would increase the affected population to 2.3 million.

FCC Commissioner Jessica Rosenworcel said she visited the Fairfax 911 center this week and was told about the “eerie quiet in the aftermath of the storms, as the calls into 911 quickly and implausibly ceased.”

Emergency officials beyond the Washington region commended the FCC review as a way to raise issues that could help prevent future outages, said Terry Hall, incoming president of the Association of Public-Safety Communications Officials.

“This is the event of the day, if you will, and very front-burner,” said Hall.

But he also said “it’s three and nearly four weeks after the storm and the [911] outages and yet we still don’t have a root cause. . . .That’s a problem in itself.”