More than 5 million people throughout Washington, D.C., Maryland and northern Virginia should have received an emergency alert on their cellphones Thursday morning as part of the largest simultaneous test conducted in the United States.

"We're doing it because in a world where there are a lot of threats out there and some that can happen with little to no notice, we need to be able to communicate with the public very quickly," said D.C. Homeland Security and Emergency Management Director Chris Rodriguez.

He said testing the system is especially important here in the nation's capital, which can be a target.

The text alert was accompanied by loud repeating tones similar to the ones you receive during an Amber Alert or a severe weather warning.

Cities and counties throughout the region issued the test alert within minutes using cell tower technology. The alert was based on a cellphone's location, so some people received several alerts if they were near multiple jurisdictions during the test.

"If there is an act of terrorism that occurred here in the District we might tell people to stay away from a certain area, that certain streets have been closed and there's police activity," said Rodriguez.

He said the alert system could be used to warn the public of a natural disaster and include tips on how to prepare. It would also help officials evacuate an area, if necessary.

"We take it very seriously to be able to test this capability make sure that it works," said Rodriguez, who spent months coordinating with 20 jurisdictions throughout the region.

This alert did not ask recipients to respond in any way, but the system does have that capability in the event of a real emergency.

If you did not receive an alert on your cellphone and you were located in or near one of the jurisdictions listed below, check your cellphone's settings. Select "notifications" and scroll all the way to the bottom to make sure your "emergency alerts" button is selected.

Emergency management officials are asking the public to take this quick survey to provide feedback as to how quickly the alert transmitted, so they can determine if any segments of the public failed to receive the message.

"Those are the metrics we're going to use to determine whether it was a success or not," said Rodriguez.

Participants in Thursday's Wireless Emergency Alert System test included:

District of Columbia

Arlington County

Charles County

Fairfax County

Frederick County

Loudoun County

Montgomery County

Prince George's County

Prince William County

City of Alexandria

City of Bowie

City of College Park

City of Fairfax

City of Falls Church

City of Gaithersburg

City of Greenbelt

City of Takoma Park

City of Manassas

City of Manassas Park

City of Rockville