On July 23, 1982, one of Boston's television stations received an ominous note about the Friday morning fires that had been plaguing the city.

"I'm Mr. Flare," it said. "You know me as the Friday firebug. I will continue until all deactivated police and fire equipment is brought back."

Yesterday the Justice Department announced the indictment of a man it said was "Mr. Flare" and six others.

They were accused of conspiracy and other charges stemming from the setting of 163 fires in Boston and neighboring cities, most of them for the explicit purpose of forcing the public to rehire police and firefighters left jobless by a statewide tax-cutting measure known as Proposition 2 1/2.

Four of the suspects, including the alleged "Mr. Flare," Gregory Bemis, 23, of South Boston, are public safety officers, authorities said. Several of them, again including Bemis, a sergeant with the Boston Housing Authority Police Department, were ordered held without bail yesterday for allegedly threatening the life of a federal agent in charge of the investigation.

U.S. Attorney William F. Weld of Boston said more indictments are expected.

Attorney General William French Smith said the blazes injured more than 270 persons, apparently all firefighters, including several who were permanently disabled. They also caused more than $22 million in property damage and cost millions more for fighting and investigating the fires.

Proposition 2 1/2, which went into effect in mid-1981 following a statewide referendum, ordered Massachusetts cities and towns to start cutting property taxes in phases until annual bills were no more than 2 1/2 percent of the market value of taxpayers' homes.

According to the 83-count indictment returned in Boston this week, the first 40 fires were set, starting in December, 1981, in trash dumpsters along lanes and alleys behind the row houses of South Boston and other neighborhoods.

When these failed to arouse enough attention, the indictment said, conspirators turned to residential and commercial buildings and resolved to set record numbers of multiple-alarm fires, sometimes as many as seven in one night.

The targets included churches, stores, office buildings, factories, warehouses, restaurants, a vacant military barracks and the Masssachusetts Fire Academy, authorities said.

Weld said the fires were usually set between midnight and 6 a.m., using a rudimentary "time-delay incendiary device" that relied on a lighted cigarette.

A few of the fires, the indictment charged, were set for profit, allegedly at the behest of Donald F. Stackpole, 28, of Scituate, and Wayne S. Sanden, 28, of Roslindale, partners in a South Boston security patrol company where Bemis was once an occasional employe.

"They provided arson security and arson patrol," Weld said. "They burned one of their own accounts to divert suspicion."

Weld said the case was the result of a two-year investigation by an Arson Task Force composed of the federal Bureau of Alcohol, Tobacco and Firearms, the Suffolk County District Attorney's office, and the Boston police and fire departments. He said BATF agents traced the "Mr. Flare" note to Bemis when they unglued the newsmagazine letters of which it was composed and found a fingerprint on the back.

The main break in the case, however, apparently came early this year when Boston police officer Robert F. Groblewski, 28, was arrested in connection with a lumber yard fire and began talking to authorities.

Groblewski was sentenced earlier this month to 12 years in federal prison after pleading guilty to setting four fires in Boston and plotting to set 25 others. He was named an unindicted co-conspirator in this week's indictment, which was returned Tuesday but kept sealed until yesterday.

Others indicted in addition to Bemis, Stackpole and Sanden, a lieutenant with the Boston Housing Authority Police Department, were Ray J. Norton Jr., 44, a full-time Boston firefighter; Leonard A. Kendall Jr., 22, of Acton, a U.S. Air Force fireman stationed in Georgia; Joseph M. Gorman, 27, of Quincy, a General Dynamics Co. rigger, and Christopher R. Damon, 27, of Hamilton, Ohio. Damon allegedly was involved in a plot to have Groblewski skip town before sentencing and to "relocate" him in another part of the country.

Weld said physical evidence in the case includes fire alarm boxes pulled off their poles, half-burned incendiary devices, photographs taken by "at least one of the conspirators" at various fires, and the "Mr. Flare" note. He said authorities also conducted electronic surveillance and recorded threats made against the life of Philip Tortorella, the BATF supervisor in charge of the investigation.

The charges, some of them carrying maximum sentences of 20 years in prison, range from arson at interstate facilities and federal buildings to conspiracy to manufacture incendiary devices, perjury and conspiracy to obstruct justice.