The Federal Aviation Administration yesterday ordered the removal of 28 unauthorized parts, mostly electronic, installed on many Boeing 727 and 737 airliners. The FAA said authorities in Seattle are considering criminal action against two companies involved.

The agency said that while it appears the parts received unauthorized certifications, there is no evidence that they present a flight hazard.

The FAA said the King County prosecutor's office in Seattle is investigating to determine if criminal action should be taken against ADS Supply Co. of Bellevue, Wash., and Air Repair Inc. of Renton, Wash.

"The source of these unapproved parts has been identified as the ADS Supply Co.," the FAA said in a statement. "All or most of these unapproved parts have apparently been represented as having been manufactured by Boeing with service tags attached, issued by Air Repair Inc., showing the parts have been modified and functionally tested."

An FAA spokesman said Air Repair is an FAA-certified shop, and added the agency possibly could lift the firm's license after an investigation.

He said Boeing at times licenses outside firms to make parts for its planes under FAA specifications, but did not do so in this case. He said Boeing discovered the unauthorized parts and notified the FAA, which cooperated with local authorities.

The spokesman said King County police authorities had conducted at least one raid to gather evidence, but did not give specifics.

The FAA said it issued the parts removal order to all airlines operating with model 727 and 737 planes. The equipment is mostly electronic and is scattered throughout the aircraft - including parts affecting the landing gear, flaps, lights, warning and heating systems.

As many as 100 aircraft might be involved, the spokesman said.

"The FAA assessment indicates that at this time there is no evidence that an immediate hazard exists with the use of these parts," the statement said. "However, at the same time we do not know that they conform to FAA requirements and further investigation is continuing."

It said an airworthiness directive issued to the airlines calls for removal within 30 days of 13 of the parts and within 45 days of the other 15.

The equipment will be replaced by certified equipment, most of it made by Boeing. FAA field personnel will monitor the removal parts to determine their airworthiness, the statement said.

An FAA spokesman said airlines confirmed to have purchased the parts included Frontier, Wien Alaska, Southwest, Braniff and American. In addition, he said, the parts "probably" also have been bought by Delta, Lufthansa and Air France.

An FAA spokesman said Boeing discovered the existence of the questionable parts in November and notified the FAA. He said the FAA issued a general notice to its field personnel Jan. 28 to notify them of a possible problem.

At that time, sources said, the FAA suspected eight parts. Since then, they said, it has identified 20 others.