Inspectors examining grounded Boeing 737s are still finding a significant number of worn fuel pump tubes, some exposing frayed wiring, the Federal Aviation Administration reported.

As of Monday night, 192 fuel pump tubes on 96 planes were inspected. Half showed signs of wire abrasion of some degree; the FAA reported chafing in 50 of the metal tubes - six of them down to bare wire."This is a pattern that we expected and this is holding true to form, so we'll see, as we continue with the inspections, what else we'll be able to learn," FAA Administrator Jane Garvey said in an interview Monday on PBS ' "The NewsHour with Jim Lehrer."

The Boeing 737 is the most widely used commercial airliner, with more than 2,700 registered worldwide. On Sunday, the FAA grounded 179 original Boeing 737 models, the 737-100 and -200 series, after an inspection of a United Airlines plane found bare wires and signs of electrical sparking in the fuel-pump tubing. Each plane has two fuel pump tubes.

Officials are concerned that a mixture of air, fuel and electricity could cause a fire or explosion. They ordered the emergency inspections and repairs that included wrapping more Teflon around the wiring or replacing the bundles and metal tubes altogether.

Critics say authorities have long ignored wiring problems in civilian and military aircraft, which could cause problems as benign as a flickering reading light to as serious as a fuel tank explosion such as the one suspected in the crash of TWA Flight 800.