"We have had been contacted by a lot of people with new information," Inspector Gary Bailey said.
"This could be from witnesses and new victims we did not know about.
"All of the information is now being assessed."
The Daily Telegraph reported Hells Angels members were using shopping malls to recruit, intimidate and rob teenagers, as well as extorting money from their parents.
Police said they had been aware of the problem for about six months and had increased patrols in the area as a result.
"This has forced offenders underground and we want the public to come forward so we can catch the offenders," Insp Bailey said.
"We have got some people who have been brave enough to come forward and tell us what's been happening."
Some parents have allegedly handed over thousands of dollars to bikies to stop their children being intimidated.
Insp Bailey said the group often targeted children who may have delved into drugs themselves.
Baulkham Hills state MP David Elliott warned parents to look out for any unusual behaviour - often an indication children were being bullied.
Insp Bailey said it was worrying that bikies could move into a family-orientated area and intimidate young people and their families.
Detectives have promised to protect the identities of anyone who comes forward with information on the issue.