A U.S. Senate panel probing the multibillion-dollar trading loss by JPMorgan Chase & Co. plans to unveil its findings at a hearing this year to press regulators to tighten the Volcker rule, according to three people briefed on the matter.

Staff members of the Permanent Subcommittee on Investigations, headed by Senator Carl Levin, have interviewed JPMorgan officials as well as examiners and supervisors at the institution's regulator, the Office of the Comptroller of the Currency, said the people, who spoke on condition of anonymity because the inquiry isn't public.

One focus of the queries is whether JPMorgan's wrong-way bets on derivatives would have been permitted under regulators' initial draft of the Volcker ban on proprietary trading, the people said. The lender lost $5.8 billion on the trades in the first six months of the year.