Hollywood star Connie Britton said she has “has no words” after the death of Hayden Panettiere, who she hailed as “bursting with brilliance”.

Panettiere, who starred as Britton’s fierce rival in country music drama Nashville, died aged 36 at her home in Greenville, South Carolina, on Sunday.

Police said the US actress, who had struggled with addiction and her mental health, was found unresponsive and in cardiac arrest, and there were “no signs of foul play or suspicious circumstances”.

A statement from Panettiere’s representatives on Monday said the star will be remembered by her family as an “incredible light” who brought “immeasurable love and joy to all who knew her”.

Tributes poured in with co-star Britton among those “heartbroken” by the loss.

The Emmy-nominated actress, who appeared alongside Panettiere in the US drama for nearly five years, shared images of her on set with her former co-star.

“This was Hayden. Bursting with brilliance, shining so bright,” she wrote.

The 59-year-old actress, also known for Friday Night Lights and American Horror Story, continued: “I have no words for this sad song.

“Just heartbreak.”

“I love you girl. Sleep easy now,” she added, accompanied by a broken heart emoji.

Emma Roberts, who appeared alongside Panettiere in films such as Scream 4 and The Architect, shared snaps of the two sharing an embrace. Roberts wrote: “Rest in peace my sweet friend.

“You are so loved and will be forever missed.”

Nico Tortorella, who also appeared in Scream 4, said: “I keep trying to write something, but there are too few words for you.”

Beneath a photo of himself with Panettiere, the 38-year-old actor added: “I love you, I miss you and I’m sorry.”

Kim Cattrall, who starred alongside Panettiere in Ice Princess, shared a picture of her with “sweet Hayden” and said she was “gone far too soon”.

Viola Davis, who featured alongside Panettiere in 2016 courtroom drama Custody, praised her as “an old, wise soul with such a deep heart” in a touching tribute on Instagram.

Bethany Joy Lenz, a long-time friend of Panettiere, said she was “crushed” by the death, and US actor Matt Lanter recounted working with her on sci-fi show Heroes.

“We always had a great time on set and tons of laughs… Man, just too young,” he wrote beneath a picture of them together.

US actress and activist Alyssa Milano, famed for roles on Charmed and Who’s The Boss?, posted a lengthy tribute reflecting on the “courage” of Panettiere and praising her campaign work for animal rights, and for standing with Ukrainians amid the Euromaidan protests.

Milano added: “Her activism was not polished or performative. It was instinctive, human, sometimes messy, often vulnerable, and always sincere.

“She was willing to be uncomfortable, to be misunderstood, and to speak before the world was ready to listen.

“Hayden was a gifted actor, but that was only part of what she gave us. She used her voice. She showed up. She cared fiercely.

“I hope that is remembered too, the way she chose to stand in the world when it mattered.”