Two leading cinema chains have faced a backlash over their decision to withdraw a film about warring gangs after a mass brawl involving teenagers armed with machetes in Birmingham.

West Midlands police is investigating what sparked the fight involving up to 100 young people but said it was “not jumping to any conclusions” or formally connecting it to the film, Blue Story.

Ch Supt Steve Graham stressed that the force did not ask for the movie to be withdrawn by Vue and Showcase cinemas after the disturbance at the Star City leisure complex on Saturday night.

Showcase had said that it would no longer show the movie at its 21 venues in the UK after Vue withdrew the movie from nearly 100 cinemas on Sunday. But following mounting criticism, Showcase said on Monday night that it was reinstating the film “supported with increased security protocols”.

A spokesman said it temporarily withdrew the film “to enable us to assess the situation” and that the decision was reversed after careful consideration and following discussions with its distributor, Paramount Pictures.

Footage on social media appeared to show people fighting on Saturday night in the foyer area of the Star City cinema, where families and children were queuing to watch Frozen II, while witnesses said some of those involved tried to force their way into screening rooms without paying.

A police spokesman said it was not believed there had been any violence inside a screening of Blue Story and that detectives were investigating whether the disorder was a “spontaneous coming together” or a pre-arranged fight.

Defending its decision to pull the film, Vue said there had been more incidents at its venues connected to Blue Story than “we have ever seen for any film in a such a short timeframe”.

It said there had been 25 “significant incidents” at Vue cinemas where the film was showing, with trouble escalated to senior management at 16 separate venues, in the first 24 hours of it showing.

A spokeswoman for Vue said a “significant incident” was “any incident that has a risk to audience members”, adding that it was awaiting clarification of the details of individual cases. She said it was unsure how many times police had been called out.

Vue said the decision was “not taken lightly or without careful consideration” and denied accusations that it was based on “biased assumptions or concern about the content of the film itself”. It described Blue Story as a “fantastic film … that has the opportunity to change lives” and that it hoped the message of the film would not get lost.

Vue added: “Despite a range of precautionary measures in place, including increased security, removal of late-night showings and reduced screenings of the film, the decision to withdraw Blue Story in its entirety was made on Saturday evening on grounds of safety alone.”

Six teenagers, including a 13-year-old girl and 14-year-old boy, were arrested after what West Midlands police described as “maybe the worst thing” its officers had seen.

The decision to pull Blue Story from cinemas provoked a fierce backlash.

Charlene White, the ITV News presenter, tweeted: “Seriously @vuecinemas?! Clearly an isolated incident at one of your locations, but you choose to blame @BlueStoryMovie & ban it from ALL your venues. Utterly ridiculous.”

Others on social media accused the cinema chains of racism. “From what I can see, Vue Cinema’s decision to ban Blue Story from all of their cinemas is at best disproportionate and at worst blatant racism,” said one user called Jonathan.

Umar Kankiya, a solicitor and co-founder of the group Dope Black Dads, which aims to challenge negative perceptions of black fathers, said he felt there was “something a little bit more sinister underlying all of this”.

He told the Guardian: “I don’t want to label any institution to be racist without firm evidence that they are … but I think it’s incumbent on them to come out and explain their reasons and why they have made the decision they have.”

Kankiya has written to Vue to demand an explanation for the withdrawal, and said the cinema chain was “withholding the ability to show black art and black artists”.

Facebook Twitter Pinterest A film still from Blue Story. Photograph: Nick Wall/Paramount Pictures

He said: “Why have Vue Cinemas made that unilateral decision to withdraw the film from all 91 cinemas across the country? I can appreciate the incident happened in Birmingham – maybe there’s an issue there that they needed to address in that particular cinema – but they then took the decision to strip it away from all the other 90 cinemas across the country and that’s where the issue lies.”

Vic Santoro, one of the actors in Blue Story, said the film did not glorify street gangs or violence and was “completely opposite to the stigma that’s been attached to it due to the unfortunate incident that took place in Birmingham”.

“It casts light on the harsh reality of London. Hopefully it serves as a deterrent to young people rather than encourage them,” he told BBC Radio 5Live.

Four of the teenagers arrested were held on suspicion of assaulting police and a fifth was held for obstructing police, all of whom were further arrested on suspicion of violent disorder.

Those five have been released on bail with conditions that ban them from leaving home at night and prohibit them from visiting Star City or any cinema in the UK.

Seven police officers sustained minor facial injuries and had to draw Tasers to bring the riot under control, as other cinemagoers screamed and ran. Many of those present were families with young children who were there to watch Frozen II.

Police said two machetes and a knife were recovered from the scene, in the Nechells district of Birmingham, and further arrests would be made in the next 24 hours.

Blue Story tells the story of a violent street rivalry in south London. It is rated 15 for very strong language, strong violence, threats, sex and drug misuse.

The film’s director, Andrew Onwubolu, also known as Rapman, said Blue Story was “about love, not violence” and that he hoped the blame for the disorder was “placed with the individuals and not an indictment of the film itself”.

He added: “Sending love to all those involved in yesterday’s violence at Star City in Birmingham. It’s truly unfortunate that a small group of people can ruin things for everybody. I pray that we can all learn to live with love and treat each other with tolerance and respect.”