A plumber's assistant was arrested yesterday and charged with attacking an Olney woman in her office, and is under investigation in connection with 17 other sexual assaults in three suburban Maryland jurisdictions, Montgomery County police said.

Joseph Nichols Kirk, 29, of the 13200 block of 11th Street, Bowie, was arrested at 2:30 p.m. yesterday at a job site in Potomac by Montgomery detectives, said Sgt. Harry Geehreng, a police spokesman.

Police charged Kirk with first-degree sexual assault in connection with the Nov. 20 attack on a 31-year-old woman at her office on Olney Sandy Spring Road, Geehreng said.

The woman was punched in the face and assaulted around 7:45 p.m. by a man wearing a stocking mask, according to a police report. Geehreng said Kirk also is a suspect in seven other sexual assaults in Montgomery County, nine in Prince George's County and one in Laurel that occurred between May 1988 and last November.

Many of the Montgomery attacks happened along the Route 29 corridor.

Geehreng said Kirk became a suspect after he was seen during a police stakeout.

Last summer, a team of 15 Montgomery County police officers was formed to investigate the sexual assaults jointly with detectives in Prince George's County and Laurel, he said.

According to a San Diego court clerk, Kirk was convicted of sexual assault there in July 1985, and was sentenced to four years in prison. Kirk was on parole until April 1989, according to a Montgomery police source, who said Kirk married about three months ago.

Kirk also is a former enlisted Navy man and a graduate of High Point High School in Beltsville, the police source said.

The girls and women in the 17 other sexual attacks in the past 30 months ranged in age from 13 to 44, police said.

They were attacked in homes, offices and dark parking lots during late evening and early morning hours, police said.

In all the cases, the attacker wore a stocking mask and rubber gloves, police said.

All the women were alone at the time of the attacks, suggesting that their assailant had monitored their habits, police said.

Geehreng said police have physical evidence linking Kirk to the Nov. 20 sexual assault, but he declined to specify what it is.

Police want to test Kirk's blood and body fluids to see whether they link him to the other assaults, Geehreng said.

The first Montgomery assault occurred May 3, 1988, on Tree Top Lane in Silver Spring. Three other attacks were reported between June and December 1988, including two in a parking lot on Prosperity Drive.

Another attack fitting the pattern was reported last June in Silver Spring. Another assault was reported last August in Silver Spring, followed by one in September in Burtonsville, police said.

In Prince George's County, police said nine sexual assaults are believed to have been committed by the same man between June 1989 and last September.

The attacks occurred in Laurel, Beltsville and Adelphi. During a two-day period in September, a man sexually assaulted three women in Laurel, police said.