Officers investigating the death of Leah Heyes want to speak to around 20 people who were around the Northallerton car park she collapsed in.
North Yorkshire Police believe the 15-year-old, from Northallerton, had taken the drug MDMA - also known as ecstasy or a "bomb" - prior to collapsing in the Applegarth car park on Saturday May 11.
Officers thanked people who had come forward but said they need more mobile phone footage that was taken on the night.
They want anyone who has footage or been shown footage, or who was passing through at the time, to come forward.
Two people have been arrested on suspicion of being concerned in the supply of class A drugs, a boy aged 17 and a man aged 18.
Both have been released while under investigation.
Detective Inspector Eamonn Clarke who is leading the investigation, said: “We have had a good response to our recent appeal for information but we know there are still people out there who have yet to come forward.
“Enquiries also reveal that there may be mobile phone video footage of the events of that tragic evening.
"This footage will be extremely helpful to our investigation and we are appealing to anyone who has footage on their phone, has been shown footage or knows of anyone who has such footage, to come forward.
“We also reiterate our appeal to anyone who was in the Applegarth car park or park on Saturday night to please contact us.
"A young girl with her whole life ahead of her and everything to look forward to has died.
"A family has been devastated and a community left in shock. It is vital that people come forward and help us find the answers for Leah’s family and friends.”
Officers have not ruled out making more arrests.
DI Clarke added: “Taking drugs appears to have become ‘the norm’ and more socially acceptable, but the fact is, it can have utterly tragic consequences and it needs to stop.
"This devastating case must be the catalyst for people in the community to stand up and help us put a stop put a stop to drug dealing.”
If you can help, contact North Yorkshire Police on 101 and ask for Northallerton CID, or call in at the front officer on Crosby Road in Northallerton.
If you wish to remain anonymous, you can pass information anonymously to Crimestoppers on 0800 555 111.
Quote incident number 12190085105.