Shobna Gulati, 52, who played Sunita Alahan in Coronation Street from 2001 to 2006, had been performing in Richard II at the Sam Wanamaker Playhouse when the incident occurred.
The actress was reportedly left unconscious after being hit by a piece of set which had fallen from the ceiling.
Shobna was rushed to hospital at the time but it’s now been reported she is recovering at home.
An audience member told The Evening Standard: “I just heard this loud bang and there was the actor lying on the stage motionless.
“It was about five or ten minutes after the interval and suddenly there was this tremendous bang.”
They continued: “There was a lot going on on the stage. It was only when we heard this bang that we realised she seemed to have been knocked out.
“Nobody moved. Then [Andoh] playing Richard II came out, she took control.”
The audience member called it “shocking” and claimed the former soap star didn’t seem “conscious”.
Another audience member said: “A piece of the set fell out of the ceiling. It hit her smack on top of the head. We thought it was fake at first.”
Onlookers said leading actress and co-director Adjoa Andoh halted the performance.
A doctor is believed to have helped Shobna until medics arrived.
Friday and Saturday’s performances of the show were later cancelled and it resumed last night where Ann Ogbomo stepped into play Shobna’s role of the Duke of York.
It’s been reported the theatre have now launched an investigation into Thursday’s incident.
A spokeswoman for the theatre told the publication: “Shobna Gulati was injured during a performance of Richard II on 28 March, but is recovering well at home
“An investigation is under way. Shobna hopes to return to the role this week.”
The production is the first Shakespeare play on a major UK stage performed by a cast of black and minority ethnic women.
Shobna went into theatre after successful stints in soaps which included her role in Coronation Street and EastEnders.
The star, who was born in Lancashire, appeared as Ameena Badawi in the BBC One soap from October to December in 2000.
Shobna is one of few star’s to have played a character in both EastEnders and Coronation Street.
Express.co.uk have contacted Shobna’s representative for comment.