The loss of 911 service in Northern Virginia and five other states after June’s derecho storm was avoidable and occurred because telephone companies did not follow their own procedures, according to a Federal Communications Commission report released Thursday.

Seventeen emergency call centers in three states received no 911 calls for an extended period after the derecho, according to the executive summary of the FCC report obtained by The Washington Post. Locally, the complete outages affected Fairfax and Prince William counties and Manassas and Manassas Park for several hours.

The FCC found that failures by various telephone companies affected service at 77 emergency call centers in six states and left dispatchers unable to receive vital information such as a caller’s location. Some problems lasted days.

FCC Chairman Julius Genachowski will propose a new set of rules for phone companies to ensure that they have backup power, perform proper testing and maintenance, monitor their 911 systems and notify local jurisdictions about outages.

“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,” Genachowski said.

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

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

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

The loss of 911 service in Northern Virginia has drawn the attention of state regulators. In all, 25 jurisdictions in Virginia — extending to the Roanoke and Richmond areas — had intermittent problems with 911 calls that continued at some locations until July 4, state regulators said.

Northern Virginia and parts of West Virginia suffered “systemic” 911 failures and there were “isolated” breakdowns in Ohio, New Jersey, Maryland and Indiana, the FCC review found.

In December, The Washington Post published an analysis showing that the Washington region’s 911 emergency network 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 troubles occurred in a system operated by Verizon, whose lines handle every 911 call made in Washington’s suburbs. No matter what telephone company a person uses to call 911 in the Washington suburbs, the call passes through Verizon’s system, which operates like a high-tech traffic cop and directs requests for help to the closest dispatch center.

Verizon routes 911 calls to 1,800 government-run answering centers nationwide, making it one of the largest such carriers in the country.

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 it blind to the crisis until local emergency workers began notifying the company that service had gone out.

Some lawmakers said last month that The Post’s findings demonstrated the need for stronger federal oversight of emergency systems nationwide, perhaps including new regulations from the FCC.

Rep. Gerald E. Connolly (D-Va.) singled out Verizon Communications for criticism.

“They have had their opportunity to do this voluntarily, and they have shirked that opportunity at every turn,” he said of Verizon in December. “To protect the public, we very clearly need the FCC.

“This is a life-and-death situation. If someone has a heart attack, 911 has got to work,” he said.

Verizon spokesman Harry J. Mitchell said at the time that the company had made many improvements and plans more. Verizon was working closely with the FCC and state regulators to examine the cause of past outages and determine what can be done to prevent future ones, he said.

“Verizon understands the critical function of 911 service and the critical role we play in successfully delivering calls to 911 from people in distress,” Mitchell said at the time. “We take this role seriously, and when an issue arises, we act quickly to investigate, correct and apply any lessons learned across our system.”

In its report, the FCC says that “above and beyond the destruction” caused by the June storm, full 911 service to communities serving 3.6 million people in affected states was disrupted “in large part because of avoidable planning and system failures.”