McCluskie - who starred in the soap for over 30 episodes as Kerry Skinner in 2001 - vanished from her London home on Thursday (March 1).
A large search has been undertaken by police in the local area, with a body being discovered in a canal in Hackney.
"We've been told the police have found the body of a woman and we're now waiting to find out if it's Gemma," a friend of the family said.
A Metropolitan Police spokesperson confirmed: "A body was found in Regents Canal near Broadway Market in East London at 2:40pm. Enquiries are under way to establish the identity of the deceased.
"A post mortem will be scheduled to ascertain the cause of death. Pending that post mortem we will be treating the death as unexplained."
McCluskie's brother Danny said: "We are all going out of our mind with worry. Her phone has been switched off since Thursday afternoon. We've not heard from her."
Over 100 people have assisted police in the search for the actress in the Bethnal Green area.
EastEnders stars Martine McCutcheon, Brooke Kinsella and Natalie Cassidy have also helped with the search on Twitter.
Kinsella wrote: "Please get in touch if you have seen her".
Gemma McCluskie's character Kerry Skinner was a close friend of Zoe Slater in the soap, and the great niece of Ethel Skinner. She also dated Robbie Jackson, who proposed to her at one stage.