West Ham will fully co-operate with the authorities in investigating the violence between rival Hammers and Millwall fans in Tuesday's Carling Cup encounter at Upton Park. Carlton Cole was the victim of monkey chants, before the England striker appeared to make a gesture back to Millwall fans.
"I didn't know he was abused by the supporters," Zola said.
Millwall boss Kenny Jackett added: "I didn't fear for my own safety."
He added: "There were no Millwall fans on the pitch. They stayed where they were supposed to.
"There were a lot of people on the pitch. The lads gathered together and came to the sides, as they should have.
"I wasn't aware of the stabbing outside the ground. I'm very sad to hear that. We've got a passionate game in this country, but when it oversteps the mark then things have to be done."
The Hammers have issued a statement vowing to punish those responsible for the "deplorable scenes".
"West Ham will fully investigate the deplorable scenes that took place during the Carling Cup tie with Millwall on Tuesday evening," the statement read.
"The club will not tolerate the unacceptable behaviour witnessed inside the Boleyn Ground and will take the strongest possible action against anyone found responsible, including life bans.
"As was the case before, during and after the match, we are co-operating fully with the relevant agencies, including the police."