Authorities investigating two incendiary packages in Maryland have more evidence to examine after a third package ignited Friday in northeast Washington, D.C.

The mailing in Washington was similar in design and shape to the packages in Maryland, according to The Baltimore Sun. The D.C. package was addressed to Homeland Security Secretary Janet Napolitano, said a department official who spoke to the Associated Press on condition of anonymity. The other packages were intended for Maryland Gov. Martin O’Malley (D) and the state’s Transportation secretary, Beverley Swaim-Staley.

Although all three parcels aroused alarm because of their fiery characteristics, they did not appear to contain explosive material. The devices in the Maryland packages each contained a small battery and an electric match, CNN said, citing law-enforcement officials.

Each of the mailings will now be examined more closely at the Federal Bureau of Investigation lab in Quantico, Va.

Already, investigators were sorting through phone calls, e-mails, and letters to try to identify potential suspects, The Sun said. One focus was disgruntled people who have made threats against state government, according to AP.

Still, much remained to be determined. “We just don’t know where this person is going with this,” said Terrence Sheridan, head of the Maryland State Police, at a news conference Friday.

Although FBI investigators are involved, the matter has not been classified as an act of terrorism, says Lindsay Godwin, a spokeswoman for the FBI’s Washington Field Office. “Until we can rule out anything, we have to have all of our assets involved,” she said, according to The Washington Post.

The Metropolitan Police Department in the District of Columbia, the Department of Homeland Security, the Postal Inspection Service, and other federal agencies are also involved in the investigation, The New York Times said.

One potential theory is that the packages were a retort to government efforts to engage the public in reporting suspicious activity. Maryland has electronic signs above highways that, among other things, have encouraged use of a state tip line. This past July, Secretary Napolitano launched an expanded, nationwide “See Something, Say Something” campaign.

At least two of the packages contained this message: “Report suspicious activity! Total [expletive]! You have created a self-fulfilling prophecy.”

Any suspects may be charged with possession and use of an incendiary device – a felony that could bring up to 20 years in prison.

According to AP, postal inspectors say that postmarks and cancellation stamps are among the ways they can determine where a package was mailed. Also, packages are tracked once they enter processing plants.

The incident with the package in Washington occurred at a postal facility, although the Maryland incidents took place in state government buildings. The Washington facility, which is not open to customers, was created after 9/11 and the anthrax scare of 2001, and it screens mail sent to various federal entities, the Post says.

The Postal Inspection Service has enhanced its capability to investigate suspicious mailings since the anthrax scare, AP notes. But only 13 cases involving dangerous devices in the mail have been reported since 2005, it says, citing inspectors.

Washington officials had put precautions in place after the two packages were discovered in Maryland. “Incidents that occur in one jurisdiction are not necessarily” limited to that place, Cathy Lanier, chief of the Metropolitan Police Department in the District of Columbia, was quoted as saying in The Sun.

Once they returned to work Friday, mailroom employees in state offices in Maryland had pictures of the incendiary packages and were urged to be extra vigilant, AP reported.

The Maryland incidents took place Thursday and resulted in minor injuries. The Washington incident occurred without injury.