WASHINGTON - US airlines have over the past three weeks removed or disabled bathroom oxygen generators on 6,000 jetliners and other aircraft over security concerns, officials said on Thursday.

The Federal Aviation Administration issued a secret directive to airlines in February to address the issue, concerned someone could exploit the privacy of the bathroom to use the generator to fuel an explosive or fire.

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No incident or threat prompted the action, the FAA said. Work on the airline fleet was completed last week, it said.

Bathrooms on commercial planes are generally located at the rear of the plane.

The directive on generators, which pump oxygen through masks that drop from the ceiling above each passenger in the event of decompression, did not apply to the main cabin. Rapid decompression on commercial aircraft is rare.

The FAA said it was working with manufacturers to develop a tamper-proof generator for the bathroom.