WASHINGTON — Officials for a California gas company involved in a deadly pipeline accident last September are acknowledging they rejected installing valves that could have automatically shut off or remotely controlled the flow of gas in event of an accident.

National Transportation Safety Board investigators questioned Pacific Gas and Electric Company employees at a hearing today about a company memo that said installing the valves would have “little or no effect on increasing human safety or protecting properties.”

Chih-hung Lee, author of the memo, said he considered only industry studies, not government studies, in reaching his conclusions.

After a Sept. 9 explosion in a San Francisco suburb, gas continued to feed a pillar of fire for an hour and a half before workers could manually shut off the flow. Eight people were killed and dozens of homes destroyed.