For the second time this week, a flash mob has robbed a convenience store in the Washington DC Area, spreading concerns that the alarming trend may have spread down from Philadelphia.

In the latest incident, ten women ambushed a Shop Express convenience store along Benning Road in northeast D.C. around 3:15 in the morning Thursday.

The girls grabbed snacks, food and drinks from different parts of the store before rushing out. Some of the girls even carried bags with them to collect small items in. None of them paid for the products.

An employee at the store told NBC Washington that they stole about $60 worth of merchandise.

Stealing is a very normal thing at convenience stores, one employee told the channel. It happens every day -- morning, evening, night. But such kind of thing I have never seen before.

The employee added that if the trend continues, he will have to close the store at night.

While the worth of the items may seem insignificant, officials are concerned that flash mobs are becoming a growing problem in the region.

Thursday's incident marked the third flash mob in recent weeks and the second in one week's time. On Saturday, a flash mob took over a 7-Eleven convenience store in Germantown, Maryland, a Washington DC suburb.

In that case, nearly three dozen individuals raided the store in the middle of the night. Investigators in Montgomery County, Maryland said they know who some of the suspects are, but are hoping people will recognize the others and call police.

Flash mobs forced the Mayor of Philadelphia, Michael Nutter, to issue curfews for under 13s and under 18s in his city after the robberies turned violent.

Nutter told CNN:

I have an understanding of what of our parents are facing, but others are in very challenging situations, and I appreciate that and understand that, but there is no excuse for young people being out so late at night by themselves and then making bad decisions and literally assaulting other citizens. I will not tolerate that.

Nutter, who is African-American, delivered a sermon at his church, Mount Carmel Baptist, telling the robbers:

You've damaged yourself, you've damaged another person, you've damaged your peers and, quite honestly, you've damage your own race.

Officials in Washington DC hope to contain the issue before it gets that far.

Watch footage of the two DC area flash mobs below:

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View more videos at: http://www.nbcwashington.com.

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