The woman aged in her 20s and boy, aged 12, are not related but both received burns after five flares were set off at the A-League soccer match held at Etihad Stadium.

Two teenage boys from Melbourne's northern suburbs have been arrested and are assisting police.

North West Metro Commander Rick Nugent said it was highly dangerous and illegal to let off flares, yet the criminal activity continued to increase.

He said last season there were eight incidents where flares were let off but since this season began, on October 10, 38 flares had been let off and 200 chairs broken.

"Flares are extremely dangerous," Commander Nugent said.

"They can burn at more than 1000 degrees Celsius and are not designed to be released in highly populated areas. As we saw last night, people can get and will get injured if this behaviour continues."

Commander Nugent said police would not tolerate flares at sporting events. This season, 30 people have been arrested at Victorian A-League soccer matches.

"Irresponsible violence and criminal damage should not be infiltrating sport in Victoria," he said.

"... We will take them before the courts, generally speaking, the offenders, as this will enable us to get a ban from the court to attend any A-League game for up to five years.

"This year, I suspect part of it is that we have young people joining the active supporter areas that are being led astray by some older, more experienced people and are now embarking upon this sort of conduct.

"It is just critical that if you are a true supporter of your club and a true supporter of this code, do not bring flares to A-league games. They are far too dangerous."

Police believe young people are acquiring the flares from boats.

"We don't believe, on our intelligence, that the flares are actually being purchased by kids at places of disposal," Commander Nugent said.

"We are of the view that these flares are often collected from the boats of parents and friends and they're brought along to the game."

He said police were working with the Football Federation Australia, the stadiums, the clubs and security to improve safety for fans but more was needed.

"There were approximately 22,000 people in attendance last night and while we know that the majority of people are well-behaved, there are a certain group of individuals within the active supportive groups who go to matches with an alternative motive.

"The troublemakers are not there to watch the match; they attend to engage in criminal activity and anti-social behaviour," he said.

Anyone with information regarding last night's incident is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at crimestoppersvic.com.au