Problems were reported across the country during the first-ever nationwide test Wednesday of the Emergency Alert System, designed to allow the president to address the American people during a national emergency.

WASHINGTON (CNN) -- Problems were reported across the country during the first-ever nationwide test Wednesday of the Emergency Alert System, designed to allow the president to address the American people during a national emergency.

Some television and radio stations did not air the planned 30-second test at all. Some that aired it stayed with the signal longer than others.

There were anecdotal reports of TV stations failing to air the message in Washington, Atlanta, New York, Southern California, and other locations. The message did not air on a cable channel being monitored in a Capitol Hill office, and in the Capitol's Radio and TV gallery.

The Federal Emergency Management Agency and the Federal Communications Commission, which ordered the test, stressed that it was designed to find flaws, and scoffed at reports the system had failed.

By late Wednesday afternoon, an FCC official, not authorized to speak on the record, said about one-third of the test participants had filed preliminary reports, and those showed that 80% to 90% of the stations received the alert and were able to rebroadcast it, which was the major criteria of the test.

The official called the failure rate of more than 10% "not insignificant," but said identifying problems "is why we have the test."

He said the glitches were found in all modes of transmission -- broadcast, cable and satellite -- and it was too early to establish patterns, if any. "We'll dig back into it," he said.

A FEMA statement issued shortly after the test made no reference to problems, except to say the agency looks forward "to working with all our stakeholders to improve this current technology and build a robust, resilient, and fully accessible next generation alerting system."

"The nationwide EAS Test served the purpose for which it was intended -- to identify gaps and generate a comprehensive set of data to help strengthen our ability to communicate during real emergencies," said Neil Derek Grace, FCC spokesman, in a released statement. "Large areas of the country received the test but some areas did not. We are currently in the process of collecting and analyzing data, and will reach a conclusion when that process is complete."

"I'm surprised about the amount of trouble I'm hearing about," said warning expert Art Botterell. "My overall impression is -- I kind of hoped for better."

Similarly, a spokeswoman at the National Cable and Telecommunications Association, which had urged FEMA to delay the test, avoided commenting on earlier reports about test problems, saying they did not yet have a "clear view" of test results. They said they hoped to have a statement later, perhaps Thursday.

"We are trying to talk to all of our cable company members to see what the results were," said spokeswoman Joy Sims.

Stations must report the results to the FCC within 45 days. The FCC says it will not release test data to the public because broadcasters worry that potentially embarrassing results could discourage participation in future tests, and test data could reveal security vulnerabilities.

Officials on Wednesday said they hope to give the public a general idea of how the EAS test performed.

The test was the first "end-to-end" national test, starting with a tone sent from a FEMA operations center in Washington that was relayed to radio stations and then broadcast simultaneously on TV and radio stations in the United States.

The Emergency Alert System is regularly used -- and tested -- to notify communities about tornadoes, child abductions and other events. But all previous tests have been local or regional, and involve the voluntary compliance of broadcasters. Wednesday's test was the first national test featuring a live "presidential" alert code, which instructed TV and radio stations that the alert took priority over all other programming.

"I think the biggest reason nobody ever tested it was because of all the concerns of what could happen and what could go wrong," FEMA chief Craig Fugate told CNN Tuesday. "We take a different approach. If we don't test it, we don't know what we need to fix."

Three weeks ago, the National Cable and Telecommunications Association asked FEMA to delay the test, saying it could cause confusion among some viewers, particularly among the deaf and hard of hearing. That's because those viewers would see the on-screen scroll stating "This is an Emergency Action Notification," but would not hear the audio message, which said, "This is a test."

"This raises the possibility that some viewers, particularly the deaf and hard-of-hearing, could mistakenly believe that the test is an actual national emergency," association President Michael Powell wrote in a letter to FEMA.

Broadcasters and satellite TV providers could superimpose a message that a "test" is being conducted, Powell wrote, but cable distributors generally do not have such equipment in place.

The FCC responded by limiting the duration of the test to 30 seconds to "reduce any potential disruptions" and minimize any possible confusion, said FEMA spokeswoman Rachel Racusen. FEMA also started a public outreach campaign to notify the hearing impaired, senior citizens, people with mental health issues and people with limited English skills.

Despite the 30-second limit, however, some stations stayed with the signal much longer.

CNN's Jim Barnett contributed to this report.