KENNER, La. – An alarm system was partially shut down the day the ill-fated oil rig Deepwater Horizon exploded in the Gulf of Mexico, killing 11 workers and setting off the massive spill, an electronics technician who was aboard told an investigative panel on Friday.

Later in Washington, the House Energy and Commerce Committee, which is investigating the spill, asked Transocean Ltd. for documents concerning safety and the condition of equipment on the rig. Transocean owned the rig, which was being leased by BP PLC. BP is responsible for cleaning up the millions of gallons of oil that have seeped into the Gulf.

Technician Mike Williams told the investigative panel that the alarm system was turned on to monitor for fire, explosive gas and toxic gas but that its sound and light alarms had been disabled. The Marine Accident Investigation panel was meeting in Kenner. It is made up of Coast Guard members and the Bureau of Ocean Energy Management, Regulation and Enforcement — formerly the Minerals Management Service.

Williams testified that he had asked before about the settings and was told the company didn’t want a false alarm waking people at night.

Williams said that if the system had been fully active, an alarm likely would have sounded before the explosion, which happened on the night of April 20. The rig sank two days later. Since then, between 94 million and 184 million gallons of oil poured into the Gulf before BP was able to cap it and stop the leak.

The House committee also cited a New York Times story this week which reported rig workers’ concerns prior to the explosion about safety and the condition of some equipment on board.

The latest in a series of hearings about the spill ended Friday in Louisiana and will resume Aug. 23 in Houston.The panel was told that the alarm system was turned on to monitor for fire, explosive gas and toxic gas but that its sound and light alarms had been disabled.