ABC News' Linzie Janis reports:

An old drug with a hot new name is being blamed for two deaths at a New York City dance festival this holiday weekend, forcing an early end to the event.

Molly, as it's now known, is a form of Ecstasy and is being linked to a recent string of overdoses.

Promoters shut down New York's multi-day Electric Zoo music festival after the deaths of two young people. Police said 20-year-old Olivia Rotondo and 23-year-old Jeffery Russ died after taking Molly. Four others are in critical condition.

Molly, short for molecule, is supposed to be the purest form of MDMA, the main ingredient in Ecstasy.

"It raises your body temperature, your heart rate goes up, your blood pressure goes up, and so it does make you more prone to heat stroke," said ABC News crime analyst Brad Garrett.

Molly has been popping up more frequently in pop culture, especially in music. At a concert last year, Madonna was caught on tape asking the crowd, "How many of you have seen Molly?" although she later said she was referring to a friend's song. Additionally, hit songs from artists, including Kanye West and Miley Cyrus, reference the drug.

Officials warn that despite the innocent sounding name, Molly is a dangerous drug.

"It could have other amphetamines in it, it could cause you to overdose, and that may well have been the case in these deaths in recent days," Garrett said.

Some law enforcement officials also said Molly is so dangerous because the people who take it tend to be recreational users and so they are more naive about its dangers.

(Getty Images/Image Source)

Rotondo reportedly told doctors she took six hits of Molly before collapsing and dying.