A number of youths turned on the cast and crew, including Patsy Palmer (Bianca Butcher) and James Forde (Liam Butcher), as they shot scenes on location at Graham Park in Colindale, North London.
The planned two-day shoot was cut short on Monday (January 21) after a gang of at least seven threw a firework at the set and shouted: "We'll cut you."
"A lot of locals came to see the shoot and most were really excited. But by mid-afternoon a pack of teenagers, a few in hoodies, began causing trouble," a source told the Sunday Mirror.
"At first they were just messing around and throwing snowballs at people watching. Then it turned nasty. They began to heckle the security staff and crew trying to film.
"They were shouting expletives and saying they wanted to have a fight. They also said they had knives and would cut up the crew."
Security managed to control the situation before things turned more aggressive. The source added: "It was clearly a group of bored lads who wanted to cause trouble.
"The cast and crew weren't bothered at first and kept filming - but then packed up. Late in the day the boys lit a firework and aimed it at the set."
An EastEnders spokesperson said: "We always get a lot of attention on location. All situations are monitored, as safety of cast and crew is our priority."