The families of three Morton Thiokol workers killed in an explosive fire at an MX missile motor assembly building have filed a $9 million negligence suit against the federal government.

The lawsuit filed Tuesday in U.S. District Court seeks $3 million each in general and specific damages for the wives and children of Jeffrey Ellis, 29, Richard Goodsell, 36, and Michael Smith, 24.The victims and two other Thiokol employees had been manually removing the steel core from a casting of a first-stage missile motor when 100,000 pounds of solid rocket propellent ignited in a fireball Dec. 29, 1987, at the company's Wasatch Operations plant 25 miles west of Brigham City.

Four of the men were killed instantly, and Ellis died 11 hours later. The Air Force concluded in a report three months after the accident that the fire was caused either by friction or static electricity.

The federal lawsuit, filed jointly by Lorene Ellis, Helen Goodsell and DiAnna Smith, contends their husbands' deaths resulted from government negligence in implementing and monitoring safety standards at the MX facility.

The plaintiffs claim government negligence in holding regular inspections of the premises to ensure that procedures were being followed by Morton Thiokol and that the government neglected to warn employees or stop work in the event non-compliance was discovered.

"The deaths of the victims were proximately caused by the defendant negligently performing or failing to perform said responsibilities," the suit alleged.

The Air Force report concluded that Morton Thiokol had failed to provide an adequate remote-control system or fully implement other safety measures recommended after a "near miss" six months earlier.

The plant's remote control system includes a video monitor to allow workers to perform the procedure form a bunker a quarter-mile away, but design deficiencies prevented them from using it as specified, the Air Force said.

Thiokol officials said such deviations were only occasional and were not known to management.

The Air Force report also said Thiokol employees neither understood nor followed grounding procedures designed to reduce static electricity and that the company routinely ignored proper procedures.

"We would take issue with the word routinely," spokesman Rocky Raab said at the time. "We would say sometimes, or occasionally."

Morton Thiokol was cited for six safety violations and fined $31,700 by the Utah Division of Occupational Safety and Health. The company vowed to appeal violations alleging serious and willful deviations from UOSH rules, but Raab said Tuesday he was not sure if the appeal was filed and the fine reduced.