(MCT) — WASHINGTON — Six U.S. senators from West Coast states urged the Justice Department on Tuesday to conduct a refinery-by-refinery probe to determine the causes of punishing gasoline price spikes earlier this year.

“We are requesting a Department of Justice investigation of possible market manipulation and false reporting by oil refineries, which may have created a perception of a supply shortage, when in fact the refineries were still producing,” said the letter sent to Attorney General Eric Holder.