Law enforcement officials are pictured entering the Maryland Department of Transport headquarters in Hanover, Maryland, in this still image taken from a video released on January 6, 2011. [Photo/Agencies]

HANOVER, Maryland - Two packages sent to state government buildings 20 miles (32 kilometers) apart released smoke and the smell of sulfur when they were opened Thursday, officials said. Two workers were slightly burned, but not seriously.

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Authorities investigated two more suspicious packages at a Baltimore courthouse which turned out to be harmless.

State officials initially said the first two packages exploded, but later said there were no blasts.

"When both packages were opened there was a reaction that caused a flash of fire, a brief flash of fire, smoke and a smell," state police spokesman Greg Shipley said. "This is not to be compared with a significant explosion that you think of when you say that word."

Mailrooms at state offices across Maryland were being quarantined until it could be determined if any other packages had been sent.

One of the packages was addressed to Gov Martin O'Malley and the other to the state transportation department.

One was opened around 12:30 pm Thursday at the Jeffrey Building, a state office building just blocks from the State House in downtown Annapolis, and another 15 minutes later at the Maryland Department of Transportation building in Hanover, near Baltimore's airport.

Shipley said the packages were small, about the size of a book. One had five holiday stamps.

The Jeffrey Building houses the state Department of Veterans Affairs, the Governor's Office of Homeland Security and the Maryland Secretary of State's office, as well as the mail room for the governor's office.

The FBI's joint terrorism task force was assisting in the investigation, the state police spokesman said, adding that the state fire marshal and a number of other law enforcement agencies also responded to the two scenes.