The attorney general is making a sweeping request for information about gasoline supplies, pricing, and maintenance shutdowns that can temporarily create shortages and increase prices, according to people familiar with the investigation. Chevron spokesman Braden Reddall said the company received a subpoena from the attorney general's office and would cooperate with the investigation. Industry officials blame high prices on California's stricter clean-air requirements, which they say add costs and make it more difficult to import gasoline from other states when there is a price spike. The group Consumer Watchdog has repeatedly called on Harris to investigate oil companies over California gas prices and welcomed news of the investigation.