BILLINGS - The Billings Police Department is conducting an internal investigation into whether officers acted properly when they used a stun gun four times on an apparently intoxicated man who went into cardiac arrest and eventually died.

None of the four officers has been suspended or placed on leave while the investigation is under way, Chief Rich St. John said Wednesday.

The review will look at whether the officers followed department procedure and took into account the hazards associated with use of a Taser on an intoxicated person when they stunned Ryan Michael Bain on Sunday night.

"The internal review case is looking at just that question, among others," St. John said.

Human-rights groups such as Amnesty International say shocks from stun guns may increase a risk of heart failure in cases where people under the influence of drugs. St. John said data exists that supports and goes against that assertion, and he could not say whether that is true.

Bain, 31, was arrested late Sunday after an off-duty Yellowstone County sheriff's deputy saw a naked man run down the street and enter a house.