A Fredericksburg, Va., woman, already charged with bombing her ex-husband's pickup truck in May, was arrested Thursday night by federal officials who said she tried to send him a homemade firebomb in the mail.

Vicki S. Dickerson, of the 500 block of Persimmon Lane, was charged in U.S. District Court in Alexandria yesterday with using the mail to send a bomb, a violation that carries a maximum sentence of 20 years in prison.

U.S. Magistrate Leonie M. Brinkema, after hearing that Dickerson intentionally cut her wrists in Fairfax County jail after her arrest, ordered her held without bond for a psychiatric examination.

Dickerson, 30, first came to the attention of authorities on May 12, the day after James H. Dickerson climbed into his pickup truck and a pipe bomb detonated under the chassis.

James Dickerson, 27, then living in Annandale, was not injured in the explosion, according to Fairfax fire officials.

Vicki Dickerson was arrested at 2:30 the next morning, when investigators found her wearing a mask and carrying various tools outside James Dickerson's home, according to law enforcement authorities.

U.S. postal inspector Thomas E. Ryan said in an affidavit in federal court that Dickerson "was attempting to rig another explosive device."

Dickerson, charged with attempted murder, burglary and use of explosives, was released in June on a $30,000 bond and was scheduled to go to trial in Fairfax Circuit Court Tuesday.

She faced a separate trial Wednesday on charges of possessing burglary tools and wearing a mask in public.

Those cases now will await the results of the psychiatric examination.

The current federal case against Dickerson began Oct. 2, when a mail carrier collected a suspicious-looking package from a mailbox at the Dumfries Shopping Center 30 miles south of Washington, according to an affidavit filed in U.S. District Court by postal inspectors.

The carrier told investigators that she noticed the box because it had a New York return address and the ink on the meter impression was blue rather than the customary red.

A piece of copper wire also protruded from a corner of the package, according to the affidavit, which goes on to describe how the parcel, which was detonated in the Dumfries Post Office parking lot, "was found to contain a homemade incendiary-type bomb."

After federal officials blew up the package, they discovered five fingerprints in the remains that matched those of Vicki Dickerson. Inspectors also determined that the postal meter strip had been "hand-drawn or traced" from a legitimate meter strip.

The return address on the package was Adult Films International on Park Lane in New York, a fictitious address.

Robert Stanley Powell, Vicki Dickerson's attorney, noted that the package was addressed to the Annandale house that Dickerson vacated months ago. "He lives in Florida, and she knows that," Powell said.

Although Powell said it takes "a fairly sophisticated person to assemble an incendiary bomb," he added that Dickerson's self-inflicted injuries and other evidence required that she receive a psychiatric evaluation.

Staff writer DeNeen L. Brown contributed to this report.