A pair of small packages, including one addressed to the governor of Maryland, erupted inside two government office buildings in Maryland and a message linked to the devices suggested they were sent by someone who was angry with the government's terror warnings, sources told ABC News.
The devices -- similar in construction to ones recently mailed to embassies in Rome and in Greece -- carried the statement: "Report suspicious activity. Total bulls..t! You have created a self fulfilling prophecy," sources told ABC News.
The devices in this case were described as powered by a small battery linked to an electric match and a switch.
In the immediate aftermath of the incident, a spike in suspicious activity reporting was seen in Baltimore and Washington. In Baltimore, two suspicious packages were found at around 3:30 p.m., according to Baltimore Police spokesperson Anthony Guglielmi. One at the courthouse turned out to be unfounded. Another that was found in the mailroom of a building that houses the Maryland Department of Health and Mental Hygiene is still under investigation.
In New York City, meanwhile, authorities issued a report on what to look out for when investigating suspicious packages or activities.
The eruptions in Maryland earlier today triggered evacuations and a federal probe into who might have sent what appears to have been incendiary bombs, which looked like a small padded envelope or a book.
The first device exploded at 12:30 p.m. at the Jeffrey Building in downtown Annapolis, which is home to several departments, including the Maryland Secretary of State and the Maryland Office of Homeland Security. It also handles mail sent to the governor's office and the package was addressed to Maryland Gov. Martin O'Malley.
The second device erupted 15 minutes later at the Department of Transportation headquarters, located near the Baltimore airport.
"When package was opened by a mailroom employee, it triggered a reaction involving smoke and a sulfur-like smell," Maryland state police said in a statement. "The employee sustained minor singing to his fingers, but refused further medical treatment."
State police spokesman Greg Shipley said there was "brief flash of fire," and the release of a sulfuric odor, but there was not a significant explosion. Shipley said "no explosive material has been found."
"This is not to be compared with a significant explosion when you think of when you say that word," Shipley added. "There was no property damage and there was obviously no serious physical harm inflicted on the employees as a result of this action."
Both packages are expected to have been connected. One of them had a return address of an empty parking lot in Washington, D.C. and was posted with five holiday stamps.
Five people were being treated for minor injuries and there were no fatalities, Ed McDonough, a spokesperson for the Maryland Emergency Management Agency, told ABC News.
All the mailrooms at other Maryland state buildings were locked down, refusing to accept any deliveries and checking the packages that were already inside the buildings, he said.
In addition, 550 people were evacuated from the two buildings, Maryland state police said. They were allowed to return to the building at about 2:30 p.m.
It is too early to tell who may have planted the devices. However the incident bore strong resemblance, including size and packaging, to a series of recent bombings in Rome and an earlier string of similar attacks in Greece. Anarchists groups claimed credit for those attacks.
Sources told ABC News that the devices that exploded in Rome were addressed to the Swiss, Chilean and Greek embassies and bore correct postage. The packages listed the sender as a cultural association, for example the Cultural Association Italy Greece, or the Cultural Association Italy Andes. They also had a return address of via Mameli 44, 00177 Rom, a nonexistent address.
The packages in Italy were described by authorities as cushioned yellow envelopes containing an interior soft envelope with a zipper that held a pyrotechnical mixture as well as metal balls for shrapnel. The devices were powered by a battery and activated when the packages were opened.
These characteristics were similar to those of devices that had exploded in Greece recently as well.
In November, book bombs were mailed to government offices and heads of state across Europe. One was found at the Chancellor's office in Berlin. Several were found in Athen's Greece where one small firebomb ignited, injuring a shipping clerk and leading police to the discovery of three more devices as well as the arrest of two bombers.
The incendiary bomb in a hollowed out book went off in the hands of a shipping clerk at Swift Mail in Athens on Nov. 1 as she was preparing to ship it to a Mexican Embassy.
According to a police report from Greece, the explosion at Swift Mail triggered a rapid police response that led to the arrest of two young men about two blocks away from the shipping firm as they were entering a metro station clad in bullet proof vests and wearing wigs. Two nine millimeter Glock pistols and five full magazines were recovered.
According to the report in addition to the bomb that exploded the men admitted to attempting to mail other bombs and appeared to have been carrying one in a plastic bag when approached by police.
The recovered bombs were addressed to Nicolas Sarkozy, a Belgian embassy and a Dutch Embassy. The one to Sarkozy was also recovered at Swift Mail. The one to the Beligan Embassy was recovered at a second shipping firm -- ACS. And the one in their possession was addressed to a Dutch Embassy.