THREE Swindon Town supporters were arrested after a flare was lit and thrown towards the pitch during the second half of Saturday's match.
The Swindon supporters were housed in the East Stand, which has a wooden floor next to where the flare, which was the size of a marker pen, landed inside the old Director's Box. It briefly set fire to the segregation netting before Fire Stewards put the flames out preventing further damage being caused.
Orient stewards identified and ejected the alleged offenders and they were arrested by waiting Police officers in Brisbane Road.
A large number of Swindon Town supporters approached club staff after the game and offered to identify the perpetrators whilst the Robins directors present have asked for their details to be passed to them.
"This was the most stupid single act I have seen inside Brisbane Road, said Orient Chief Executive Matt Porter.
"These individuals endangered the lives of the 1580 supporters from both teams inside the stand with their idiotic actions and it could have ended up much, much worse.
"The Club will fully assist in the Metropolitan Police's investigation in to the incident and will be pressing for the strongest possible punishments for the offenders.
"Thanks to the Swindon supporters who offered to assist us in identifying them - they were outraged that their lives had been put in danger and want these people held to account for their actions."