WASHINGTON - A package addressed to US Homeland Security Secretary Janet Napolitano ignited on Friday at a postal facility in Washington, D.C. but was quickly extinguished and no one was injured, authorities said.

A postal worker was tossing mail into a bin when the package was discovered "popping, smoking and with a brief flash of fire," Cathy Lanier, chief of the Washington Metropolitan Police Department, said during a news conference.

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The package was addressed to Napolitano and was believed to be similar to others found in two incidents involving packages delivered to Maryland state offices on Thursday, a Department of Homeland Security official said. No one was seriously injured in those incidents.

"Initial reporting indicates this incident bears characteristics similar to the flaring package incidents at two Maryland state facilities yesterday," the DHS official said.

Lanier and other officials declined to provide further details about the incident in Washington. Napolitano's primary office is across town from the mail facility.

Security officials said the incidents were not believed to be the result of Islamist terrorism. Napolitano returned late Thursday from a weeklong trip to Afghanistan, Qatar, Israel and Belgium to discuss terrorism and transportation security.

Her office is about eight miles away from the mail facility, which screens and handles mail and packages sent to federal government agencies. It was set up in the wake of the Sept. 11, 2001 attacks and 2001 anthrax attack.

The mail incidents this week revived memories of letters laced with the deadly anthrax sent nearly a decade ago to top US lawmakers in Washington and to members of the news media. Those letters killed five people and sickened 17 others.

The postal facility is located in an industrial area of the city, not near tourist districts, the White House or Capitol building. The FBI, postal inspectors and local police were investigating the latest incident.

On Thursday, two packages erupted in smoke and flames in the mailrooms of two Maryland state government buildings but no one was seriously injured.

At least one of the packages in Maryland contained a message complaining about electronic highway road signs that ask motorists to report suspicious activity, said law enforcement and intelligence officials.

Napolitano has spearheaded a campaign to encourage people to report suspicious activity they see that could be linked to terrorism or an attempt to attack the United States, dubbed "If You See Something, Say Something."

She has recorded messages requesting vigilance and they play on the D.C. transit system and in Walmart stores across the country.