WASHINGTON (DC News Now) — Police across D.C. and Maryland are investigating several bomb threats over the past two weeks. Though all have turned out to be hoaxes, law enforcement has to take them seriously.

Former FBI Special Agent Kenneth Gray says the reality is people making these threats over the phone or email may be across state lines.

The FBI says making a hoax threat against a school or other public place is a serious federal crime.

Several bomb threats have disrupted classes, shopping malls and parks across the D.C. area recently.

A bomb threat at Montgomery Mall on August 18 and a bomb threat at the Bullis School on August 22 are believed to be connected to the same person calling in the threat. Both turned out to be nothing.

“Bomb threats can be actually threats leading to an actual bombing. And so they all have to be taken seriously,” Gray said.” They all have to require certain steps to be taken for it. So this is not just a game that’s being played.”

Gray, a University of New Haven senior lecturer in the Department of Criminal Justice, says bomb threats often set off a series of copycats.

“We especially see that in schools, that is one person calls in a bomb threat at one school, you end up seeing bomb threats being called in within days at other schools,” Gray said.

A bomb threat at John F. Kennedy High School in Wheaton-Glenmont on Tuesday morning turned out to be nothing, as did a bomb threat through email that shut the Smithsonian National Zoo down for the day.

The FBI often gets involved to help track down the people responsible, using information from phone providers, IP addresses and more.

“Often with the technology we have today, some of these types of threats that come in, you get pretty quick notification of where the cause originating from,” Gray said.

Cyber security consultant Reggie Bullock said most IT departments have routines in place to help identify where messages are coming from. He says one of the first steps is to identify if the threat is specific or part of a pattern.

“We do a lot of research, so we’ll take these IP addresses and we’ll copy them and put them into databases, known databases of hackers, scammers and things like that. And so what we’re looking for is a quick hit to say, boom, we know that this particular attacker is been doing this in 50 states and 30 countries,” Bullock said.

The FBI says issuing a threat—even over social media, via text message, or through e-mail—is a federal crime and those who post or send these threats can receive up to five years in federal prison or face state or local charges.