CNN  — 

Parents are now cooperating with health officials after a teen party in Middletown, New Jersey, led to a Covid-19 cluster in the area.

More than 20 teens tested positive for the coronavirus after attending a house party on July 11, Middletown Health Department spokeswoman Tara Berson tells CNN.

The partygoers ranged in age from 15 to 19 years old, Berson said.

Earlier this week, health officials attempted to contact parents and teens for contact tracing, but said their response was “less than satisfactory.”

Parents have since been more responsive, a statement from Middletown Health Department Director Rich DeBenedetto says in part, “We have received a large response from parents who weren’t aware of the situation and thankful that they could address it with their kids and ensure they get tested/quarantine.”

In a press conference on Thursday, Gov. Phil Murphy warned residents, especially young people, not to congregate indoors.

“Congregating, even if you’re a young person and you’re healthy – and you may be asymptomatic and you think you’re invincible – you can’t congregate closely indoors,” Murphy said.

The governor is now urging anyone who may have attended the party to come forward and speak with health officials.

“To be perfectly clear this is not a witch hunt to root out anyone who was drinking underage although we do not condone underage drinking, and remember folks, it is illegal. But this is not what this is about. This is a race against the clock to ensure that everyone who may have been exposed to coronavirus is identified before they infect anyone else,” Murphy said.

CNN’s Laura Dolan contributed to this report.