Months after widespread 911 outages in the Washington area, federal regulators said Thursday that they still have grave concerns about whether Verizon Communications has improved its system, citing the company’s inability to immediately produce maintenance records or adequately explain its own phone circuits.

In a severely critical report that focused on phone problems after June’s derecho storm, the FCC also said Verizon told federal regulators that a crucial generator had passed an inspection days before the storm, although, in fact, it had failed.

In response, the Federal Communications Commission said it would move to require telephone companies nationwide to strengthen their 911 systems in an effort to reduce potentially life-threatening outages.

The FCC review discovered that the storm’s effect was far more severe than previously known. It knocked out or restricted phone service to 77 emergency call centers in six states and affected 3.6 million people, most of them in Northern Virginia.

The report singled out Verizon Communications, saying the FCC continues to have serious concerns about the company’s maintenance and “actual repair practices.”

Report: Impact of the June 2012 Derecho on Communications Networks and Services

Among its new findings, the FCC reported that although internal procedures at Verizon apparently required monthly testing of backup generators, tests had not been done at an Arlington County site since “at least 2011.”

“It’s actually worse than we knew,” said Rep. Gerald E. Connolly (D-Va.). “It is a stunning report and a very strong rebuke to Verizon’s performance — or lack thereof.”

He added, “Verizon has some real explaining to do here.”

Verizon lines handle every 911 call made in Washington’s suburbs. No matter which telephone company is used to call 911 in the D.C. suburbs, Verizon routes the call to the closest dispatch center.

Verizon executives said that they have replaced and repaired generators in Arlington and Fairfax County that caused the widespread local outages and that they continue to upgrade power systems elsewhere in the region. Company officials have also tightened and streamlined maintenance procedures and training, and they have met with local 911 officials at government centers to improve communications.

While commending those efforts, the FCC said Verizon “has much more to do,” including checking whether other parts of the system throughout the country have flaws similar to those uncovered in Virginia.

Verizon “takes seriously” its role in the 911 system, said Anthony Melone, the chief technology officer, saying the company has “acted diligently and decisively” to resolve issues.

In addition to Verizon, the report covers the performance of three other companies in delivering 911 calls to emergency centers.

There were isolated problems with 911 service and regular phone service in Maryland, Ohio, Indiana and New Jersey. But the disruptions were systemic in West Virginia and in Northern Virginia.

‘The bottom line’

“Here’s the bottom line: We can’t prevent disasters from happening. But we can work relentlessly to make sure Americans can connect with emergency responders when they need to most,” FCC Chairman Julius Genachowski said.

In all, 25 jurisdictions in Virginia — extending to the Roanoke and Richmond areas — had intermittent problems with Verizon’s routing of 911 calls that continued for days after the June 29 storm. Verizon’s troubles stopped all 911 calls from reaching centers in Fairfax and Prince William counties and Manassas and Manassas Park.

“As a region, we may have been presuming too much about Verizon’s oversight on its own system, which is the part we don’t control,” said Jeffrey Horwitz, deputy commander of Arlington’s Emergency Communications Center.

In December, The Washington Post published an analysis showing that Verizon’s 911 service in the Washington region had suffered widespread systemic failures over the past two years. The Post’s study documented that there had been at least 11 outages since July 2010 in Virginia and Maryland, at times leaving residents who rushed to report life-threatening injuries instead listening to busy signals. Some outages blocked all calls in a particular area; others restricted the number of calls or deprived authorities of location data and call-back numbers.

The loss of 911 during the derecho was avoidable and occurred because telephone companies in the six states did not follow their own procedures, the FCC report said.

“This report validates Fairfax County’s strong concerns about Verizon’s performance following last year’s derecho,” said Sharon Bulova (D), chairman of the Fairfax County Board of Supervisors. “The kind of breakdown that the FCC report addresses must never happen again.”

Telecommunications experts said the FCC report was uncharacteristically tough.

‘Pretty strong language’

“For the FCC, this is pretty strong language,” said Steve Augustino, a Washington telecommunications lawyer. “It is unusual for the commission to make statements like this in a report.”

After Hurricane Katrina in 2005, the FCC proposed tightening rules to make service more reliable, including requiring backup power at cell towers. But major wireless carriers challenged those rules in court, and they did not take effect.

The outages in the Washington area during the past two years were caused by a variety of problems and could not be traced to a single factor, The Post’s review found.

The problems included struggles to maintain equipment, technical glitches and automatic alarms going unheeded.

During the derecho, Verizon acknowledged, backup generators did not start and repair workers were slow to find the problems.

The failures cut service for 911 callers and also took down Verizon’s monitoring system, leaving the company blind to the crisis until local emergency workers began notifying it that service had gone out.

The 911 failures that occurred in June “are unacceptable, and the FCC will do whatever is necessary to ensure the reliability of 911,” Genachowski said.