Tesoro Corp. is making progress in a review of its Hawai'i refinery operations that it announced in March.

The company, on a conference call with analysts, said a lot of effort was going into determining how it could improve profitability of the facility on a regular basis.

Bruce Smith, who retired as Tesoro's chief executive officer yesterday, said the company thinks it can unlock additional value at the refinery.

"I think it's sort of multi-functional," said Smith, according to a transcript of the call. "And I think we'll end up being successful in coming back to describe some of the things that we've been able to do."

Tesoro has looked at ways to improve returns from the Campbell Industrial Park refinery, which is one of the least profitable of the seven refineries it owns.

It previously said it might shutter refinery operations and maintain the facility as a distribution terminal.

Tesoro also has looked at refining biofuel at the Hawai'i facility.