Leah Heyes died after she collapsed in a car park in Northallerton, North Yorkshire, at about 9.30pm on Saturday night.
On Tuesday, North Yorkshire Police said an 18-year-old man had been arrested on suspicion of being concerned in the supply of class A drugs.
This followed the earlier arrest of a 17-year-old boy in connection with the incident.
A spokesman said: "Last night, a second arrest was made by officers investigating the circumstances of Leah's death.
"An 18-year-old man was arrested and interviewed. He has since been released while under investigation.
"The 17-year-old who was arrested previously has also been released while under investigation."
Earlier, the spokesman said: "We believe that Leah had taken the drug MDMA - also known as ecstasy or a 'bomb' - prior to collapsing and we reiterate our warning to anyone who uses drugs of the potential consequences."
The force said officers are continuing to investigate to determine the circumstances surrounding Leah's death on Saturday night.
A post-mortem examination will be carried out to determine the cause of her death.
On Sunday, Detective Inspector Jon Sygrove advised anyone who had bought MDMA recently to be cautious about taking it.
He urged anyone who had taken the drug and was feeling unwell to seek medical help immediately.
Police have asked anyone who was in the area at the time, or has any information about the events on Saturday night, to come forward if they have not already done so.
Anyone with information is asked to call North Yorkshire Police on 101, select option two and ask for Northallerton CID, or contact Crimestoppers anonymously on 0800 555111.