THE SCENE: Firefighters survey the crash site at Santa Monica Airport in September. (Photo courtesy David J. Hawkins)

THE SCENE: Firefighters survey the crash site at Santa Monica Airport in September. (Photo courtesy David J. Hawkins)

SMO — Rep. Henry Waxman, D-Santa Monica, sent a letter Monday to the National Transportation Safety Board (NTSB) calling for an expedited investigation of the September crash that left four dead at Santa Monica Airport.

The message was a response to NTSB Acting Chair Deborah Hersman, who previously wrote that she “believe[d] safety was compromised by stopping this investigation” during October’s federal government shutdown.

“I am concerned about any impact on your ability to conduct a thorough investigation of this fatal crash,” Waxman wrote. “I urge you to redouble your efforts on this investigation to make up for any impediments caused by the shutdown.”

NTSB representatives did not offer an official response to Waxman’s letter, but reiterated that they are working hard to conclude the investigation.

“We continue to conduct as thorough of an investigation as we would in any of our investigations,” said spokesperson Keith Holloway. “An investigator actually has been working with the Federal Aviation Administration (FAA), the air frame manufacturer (Cessna) and engine manufacturer (Williams International).”

The inclusion of Cessna and Williams International to the investigation does not imply that the companies are responsible for the crash, however.

“Standard procedure for active investigation is to loop in multiple parties,” said FAA public affairs officer Ian Gregor.

The preliminary report released by the NTSB in late October found that the airplane’s tires showed no unusual damage and that no debris was on the runaway at the time of the crash. It could be 18 months before the investigation is completed, Holloway said.