The family of a 3-year-old District girl who was fatally injured in a fall on a Metro escalator last month sued the transit system and the escalator manufacturer for $90 million yesterday in U.S. District Court here.

The complaint alleged that the victim, Melissa Gilbert of 723 Madison St. NW, was strangled in the Jan. 26 accident at the Minnesota Avenue Metro Station. Authorities said the strings of the girl's parka apparently became caught in the escalator's treads after she fell on the steps.

Melissa and her twin sister, Melanie, were on their way downtown with their grandmother, Gertrude E. Truesdale, to buy roller skates for the girls' birthday when the accident occurred, according to officials.

The complaint alleged that Metro and the escalator maker, Westinghouse Electric Corp., were negligent in failing to provide "adequate safeguards and warnings" concerning the escalator and "no adequate methods of stopping the escalator."

A Metro official said yesterday the agency had not seen the lawsuit and would have no comment. Westinghouse officials could not be reached immediately for comment.

Metro authorities said after the accident that they would launch a study of possible ways to improve the safety of the system's station escalators.

"They [Metro officials] say they have an injury rate of 1.6 per million riders," said lawyer John P. Coale, who filed the lawsuit. "A million people ride the system in a week. That means that one person per week is getting nailed."

The escalators are equipped with a stop button located near the base of the structure, according to Metro officials. The machines can also be stopped by an attendant in the station booth, or by giving the escalator sides a hard kick, officials said.

But a Metro spokeswoman said last month that none of the methods is advertised to the public because officials fear that a sudden stop might pitch escalator riders off their feet.

"Metro says the stop button might be abused" if it were more accessible, said Coale. "But there are stop buttons in thousands of elevators in this town that are not misused."

Metro deputy general manager Theodore Weigle Jr. said shortly after the incident that the Minnesota Avenue station escalator was stopped in "probably a matter of seconds, or a minute." He said it took 20 minutes to free the girl because she was so tightly pinned to the treads.

Westinghouse regional manager director Ronald Boice said at the time that he had not heard of another escalator fatality in his 20 years with the firm.

The lawsuit was filed on behalf of Gilbert's father, Claude, of Bladensburg, her mother, Denise Wright,of the Madison Street address, her grandmother and her twin sister.

Besides negligence, the complaint alleged that Metro and Westinghouse were liable for wrongful death and the infliction of emotional distress. Melissa's grandmother and sister "witnessed with horror and terror" the girl's strangulation, the suit contended.

The suit seeks $20 million in punitive damages, claiming that Metro and Westinghouse knew or should have known that the escalator was dangerous and failed to install safety devices, disregarding "their obligation and duty to do so."