The three young District women whose bodies were found on a rural Maryland road early Saturday morning all died of gunshot wounds, officials said yesterday.

Autopsies showed that Tamika Black, 19, and Tanji Jackson, 21, were both shot twice, said Donald Wright, deputy chief medical examiner for the State of Maryland. Mishann Chinn, 23, was shot once, Wright said.

The victims were all shot in the head or upper body, Wright said.

The three women also had bruises consistent with blunt-force trauma, Wright said. But medical examiners were not certain whether those bruises were sustained from blows struck while the women were alive or whether the injuries occurred after the women had been fatally shot, Wright said. The bruises could have happened when the women's bodies were thrown to the road, Wright said.

"Two of the ladies also had injuries consistent with being run over by a vehicle, but the cause of death is the gunshot wounds," Wright said. The bodies were fully clothed, and there was no sign that any of the victims had been sexually assaulted, police and Wright said.

Because the bodies were discovered on federal land, U.S. Park Police have been investigating the case. The bodies were found by a motorist about 4 a.m. Saturday in the southbound lane of Route 197 in Beltsville. The location is north of the National Agricultural Research Center and south of the Patuxent Wildlife Research Center.

As of yesterday, investigators had not determined whether the victims were killed where their bodies were found or slain elsewhere and dumped on the road. It was not known whether two of the victims had been run over by the killer or killers or by motorists passing in the dark and rain.

Investigators also were trying to determine whether the three women, who had been friends for about five years, ever arrived at the Mirage, a nightclub south of Capitol Hill where, according to the mother of one of the victims, the three were heading Friday night. Joyce Gaston, the mother of Black, said her daughter left their home in the 100 block of Tuckerman Street NW and got into a car with the two other victims and two men about 11 p.m. Friday.

Gaston said she did not know who the two men were. Park Police officials said they do not know where the women went or whom they were with after 11 p.m..

Investigators have heard conflicting accounts of what the women did Friday night, said Officer Greg Lehman, a Park Police spokesman. "We've gotten quite a few calls and possible sightings," Lehman said.

Also, no motive has emerged. The victims were not sexually assaulted. Their purses were found near their bodies, and investigators said they do not believe they were robbed. None of the victims had a criminal record in the District or Prince George's County, according to court records.

Police and prosecutors in the District and Prince George's said they could find nothing to indicate that any of the three were witnesses in a criminal case in those jurisdictions.

In another development, a D.C. police official said Park Police have accepted an offer by D.C. homicide investigators to assist in the hunt for the killer or killers.

Homicide detectives assigned to cases in the 1st Police District will assist Park Police, said Inspector Clarence Dickerson, the D.C. police department's chief of detectives.

The Mirage nightclub is in the 1st District. D.C. homicide detectives assigned to the slayings in that district have investigated cases that occurred inside and outside the club.

"The women were residents in the city, they were visiting clubs in the city; there is a chance someone they met in the city could become a suspect," Dickerson said.

D.C. police also want to stay abreast of the investigation because of the possibility that the women were killed in the District, in which case D.C. homicide detectives would take over the case, Dickerson said.

Little could be learned yesterday about Jackson. The Park Police gave as her home address a District street and block number that does not exist.

Black and Chinn lived in middle-class neighborhoods in Northwest and Southeast Washington, respectively.

For the last three years, Black worked as a teacher's aide at National Presbyterian School, an independent school for kindergarten through sixth grade on Nebraska Avenue NW.

Black graduated from Eleanor Roosevelt High School in Greenbelt in 1994. Jackson attended the school but did not graduate, leaving in the ninth or 10th grade, according to former Roosevelt students.

Doug Elliott, president of the board of trustees at the National Presbyterian School, said Black was planning to return to school and pursue a career in teaching.

Chinn occasionally worked in a neighborhood day-care center near her home, in the 2900 block of Fort Baker Drive SE.

Former high school classmates of Black's and Jackson's said that the Patuxent Wildlife Research Center, which is near where the bodies were found, was known as a "lover's lane" among some Roosevelt students.

Park Police asked that anyone with information on the case call them at 202-619-7310. Staff writers Amy Argetsinger and Avis Thomas-Lester and special correspondent Jayson T. Blair contributed to this report.