UPDATED 11/16/11 8:05 a.m.

CHICAGO (CBS) — Police Supt. Garry McCarthy confirmed Tuesday that an internal investigation is underway after a Marine Unit diver accused a Fire Department captain – and son of a former Fire Department commissioner – of knocking him to the ground earlier this month as they tried to rescue two men from the Chicago River near Goose Island.

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As CBS 2’s Kristyn Hartman reports, the police diver called the fire captain’s actions totally out of line.

LISTEN: WBBM Newsradio’s Mike Krauser reports

It all started with two departments on the same mission: to rescue two people from drowning in the Chicago River. But things got ugly when both police and fire marine units responded to the scene.

On Nov. 1, the scene of a river rescue was also the scene of an ill-tempered encounter.

Police Marine Unit Officer Joe Smith has filed a report alleging Fire Capt. Mark Altman was the aggressor in a physical confrontation during the emergency response. Altman is the son of former Fire Commissioner Ed Altman.

Monday night, Capt. Altman’s wife said “It’s all gossip. It’s all people making up stories.”

Smith offered a totally different take on Tuesday. In a statement, he said “His (Altman’s) actions were totally out of line. I was there to rescue and investigate why two people were in the river. Any ordinary citizen would have been arrested on the spot. He is responsible for his actions, regardless of his connections.”

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Smith said Altman shoved him so hard, he fell to the ground.

No one has said what provoked the confrontation, but because of the rescue operation at hand, a source said the decision was made to handle it later – thus the case report recently filed by Smith.

CBS 2 could not get access to that report or much additional information about the confrontation.

“It’s an internal investigation … we’re not going to talk about it now,” McCarthy said Tuesday.

Smith said, “My complaint is against the one individual, not the entire Chicago Fire Department.”

Altman did not respond to calls for comment. Before his wife ended an interview on Monday, she said she knew of no case report and referred other questions to the Fire Department.

A Fire Department representative said there is an ongoing investigation into the confrontation.

Meanwhile, WBBM Newsradio’s Mike Krauser reports the Better Government Association has begun a probe of the investigation, which is unusual for an alleged battery.

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In an article written in conjunction with the Chicago Sun-Times, the BGA says Joshua Dennis, the executive assistant to Fire Commissioner Robert Hoff, sent an e-mail to department brass saying no requests by the city Inspector General are to be honored unless approved by the Fire Commissioner.