(Reuters) Record-high refining margins have renewed buyer interest in ExxonMobil Corp’s smallest oil refinery, a 61,500 barrel-per-day plant in Billings, Montana, said people familiar with the matter.

U.S. profit margins for processing crude into gasoline, diesel and jet fuel hit five-year highs this month, reviving the plant’s appeal. Rising travel and fewer refineries from pandemic-shutdowns have U.S. gasoline prices headed toward an average $6 a gallon this summer, say analysts.

At least three companies and a private investment group have shown renewed interest in the refinery this year, which returned to full production this week for the first time since a March 27 fire, the people said.

“We don’t comment on rumors,” said ExxonMobil spokesperson Julie King.

The nation’s largest refiner by volume, Marathon Petroleum Corp, along with Par Pacific Holdings  and CVR Energy are potential buyers, the people said.

Marathon Petroleum spokesperson Jamal Kheiry declined to comment. Par Pacific and CVR did not reply to requests for comment.

At least one interested buyer is said by the sources to be discussing the terms of a deal with Exxon for the refinery and could announce a sale agreement sometime this summer.

ExxonMobil put the facility on the market to reduce its U.S. refining footprint to four plants: a trio of refineries in Baton Rouge, Louisiana, Baytown and Beaumont, Texas, which are among the nation’s largest and have adjoining chemical plants, and a 251,800 barrel-per-day refinery in Joliet, Illinois.