Federal authorities are preparing to bring charges in connection with an October arson that killed an East Baltimore family who tried to fight drug dealing in their neighborhood, a move that would mark the latest instance in the past year where U.S. prosecutors have stepped in to handle the city's worst violent crimes.

Maryland U.S. Attorney Thomas M. DiBiagio had scheduled a news conference for yesterday to announce what his office called "a significant development in an arson investigation." Law enforcement sources said the case involved the Oct. 13 fire that killed Angela and Carnell Dawson and their five children.

The news conference was canceled after yesterday's snowstorm closed offices in U.S. District Court in Baltimore. It was not immediately rescheduled, and Assistant U.S. Attorney Virginia B. Evans, a spokeswoman for the office, said it would be inappropriate to comment on what case the announcement was expected to address.

DiBiagio had previously acknowledged that prosecutors from his office were consulting with Baltimore State's Attorney Patricia C. Jessamy to determine whether charges in the case should be brought in federal court -- where defendants would face a less forgiving jury pool and possibly harsher penalties than in the troubled city court system.

State prosecutors have charged 21-year-old Darrell Brooks, a neighbor with a long history of run-ins with city police, with multiple counts of first-degree murder. His arrest fanned community concerns about a state court system perceived as not having done enough to keep those accused of crime jailed.

Brooks has faced a string of armed robbery, assault and other charges, dating at least to 1998. State officials have said that Brooks could have been jailed months before the fire that killed the Dawson family because he had failed to report to his probation officer as required.

In the Dawson family's case, Brooks is being held without bail. The public defender assigned to represent him could not be reached yesterday to comment.

Police have said the October fire in the 1400 block of E. Preston St. appeared to have been set in retaliation for Angela Dawson's complaints about neighborhood drug dealers.

Dawson, 36, died in the blaze along with her children: Keith and Kevin Dawson, 9; Carnell Dawson Jr., 10; Juan Ortiz, 12; and LaWanda Ortiz, 14. Carnell Dawson Sr., 43, jumped from a second-story window to escape the fire. He was critically injured and died of his injuries a week later.

If the case surrounding their deaths moves to federal court, it would join a growing list of high-profile city crimes that have been transferred from the state court system to U.S. court since DiBiagio took office a year ago.

Under DiBiagio, the U.S. attorney's office has brought charges that could carry the death penalty in two fatal carjacking cases and against the leaders of a drug gang believed responsible for a deadly shooting at a Memorial Day block party last year.

Federal authorities also gained a conviction on gun and drug charges against Eric D. Stennett, who was acquitted in state court of killing a city police officer and arrested last spring in a street-corner bust.

In September, U.S. prosecutors charged the alleged ringleaders of one of West Baltimore's most violent drug gangs -- the Lexington Terrace Boys -- with carrying out the slayings of six people, including one man who prosecutors said was killed to prevent him from testifying about a double homicide.

The decision to prosecute each of the cases in federal court was made in concert with Jessamy's office, officials say.