"ER" actress Mary Mara's caused of death was confirmed on Thursday to be "an accident" and "due to asphyxiation, and water drowning" while she was swimming in a New York river over the weekend. Mara was 61.

"The Jefferson County Medical Examiner’s Office performed a post-mortem examination on the decedent and determined that Mary Mara’s manner of death was an accident, due to asphyxiation, and water drowning," New York State Police Officer Troop D Public Information Officer Jack Keller told Fox News Digital. "The investigation is continuing."

Mara died on Sunday, June 26, while swimming in the St. Lawrence River in New York. State Police responded to 33753 Old Farm Road in Cape Vincent, Jefferson County, on a report of a possible drowning on Sunday at 8:10 a.m.

Mary Mara drowned in St. Lawrence River

"ER" actress Mary Mara during the 2006 Los Angeles Film Festival. (Getty Images)

‘ER’S MARY MARA DEAD AT 61, ACTRESS DROWNED WHILE SWIMMING IN NEW YORK RIVER

"When Troopers, along with Cape Vincent Fire and Ambulance, arrived on the scene, they discovered a female deceased in the St. Lawrence River," a release from the department stated. 

"The victim has been identified as 61-year-old Mary T. Mara from Cape Vincent, NY."

Preliminary investigations suggested Mara drowned while swimming and her body showed "no signs of foul play."

The "Law & Order" actress' representative, Craig Dorfman, confirmed her death to Fox News Digital on Monday: "Mary’s body was found this morning in her beloved St Lawrence River. She drowned while swimming.

Mary Mara starred in film and television roles

Mary Mara, pictured in 2006, died on Sunday, June 26, while swimming in the St. Lawrence River in New York. She was 61. (Matthew Simmons)

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"Mary was one of the finest actresses I ever met. She had a terrific sense of humor and a unique outlook on life. I still remember the first time that I saw her onstage in Mad Forest in '92. She was utterly captivating, well loved, and will be missed."

A family spokesperson said Mara was staying at her sister's summer home. The property fronts the river outside the Village of Cape Vincent, in the Thousand Islands region, where the St. Lawrence separates Canada and the U.S.

Mara, a New York native, began working in the entertainment industry in the late '80s, and had recurring roles on "Nash Bridges," "NYPD Blue," "Hope & Gloria," and "The Practice."

She worked with Sandra Bullock on "Love Potion #9," Michael J. Fox in "The Hard Way," Billy Crystal in "Mr. Saturday Night," John Travolta in "A Civil Action," and Mandy Patinkin in "Criminal Minds" and "True Colors."

Mary Mara attended a film premiere in 2001

Mary Mara, pictured in 2001, had a host of guest roles under her belt with a 32-year career in the entertainment industry. (J. Vespa)

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She appeared in 1989 with Michelle Pfeiffer, Jeff Goldblum, Mary Elizabeth Mastrantonio and Gregory Hines in a New York Shakespeare Festival production of "Twelfth Night," and in 1990 co-starred with William Hurt in a Yale Repertory Theatre performance of Anton Chekhov’s "Ivanov."

Mara worked on episodes of the popular television shows "Ray Donovan," "Shameless," "Dexter" and "Lost."

Her last appearance was in the film, "Break Even," released in 2020. 

Mara is survived by her stepdaughter, Katie Mersola; sister, Martha Mara; another sister and a brother-in-law, Susan Mara and Scott Dailey; and nephew, Christopher Dailey.

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Fox News' Larry Fink contributed to this report.