An undercover narcotics investigation led to the seizure Thursday night of several million dollars worth of a drug in popular use at dance clubs and music festivals.

Clayton County police spokeswoman Danielle Rosa said near 50 pounds of MDMA, a form of Ecstasy that goes by the street name “Molly,” was seized at a home in the 5900 block of Monetery Drive near Morrow.

Police also confiscated 14 firearms and three vehicles, and made two arrests, Rosa said. Police have not released the names of those arrested.

Rosa said the seized Molly has a street value of about $3 million.

“The drug offers users a 6-24 hour euphoric state of mind,” she said. “However, the long term health effects could include brain damage and kidney failure.”

Last weekend, an electronic dance music festival in New York City was cut short after two festival-goers died and four others were hospitalized after apparently overdosing on Molly.

A similar multi-day music festival, Tomorrowworld, will be held at the end of this month on a Chattahoochee Hills farm in south Fulton County.

“Molly is emerging as the new designer drug parents need to be aware of,” said Dr. Gaylord Lopez, director of the Georgia Poison Center. “What seems benign is really not benign. Parents need to be on the lookout for the language their kids may be using. You could hear, ‘Hey, anybody hear from Molly’ and that can be code for ‘did anyone score Molly?’ ”

Short for molecule, Molly is often referred to as the “hug drug” because the user may “get into touch with themselves and other people,” according to Gary Gudelsky, a professor at the University of Cincinnati who has researched MDMA’s effect the brain for more than two decades.

Molly is making the rounds in pop culture with artists including Kayne West and Rihanna mentioning Molly in songs.

In 2011, there were 62 emergency room visits across the state involving Ecstasy, according to the Georgia Poison Center. In 2012, there were 57 cases. This year by June, there were already 46 cases reported, putting the state on pace to far exceed recent years, according to Lopez. Lopez said the vast majority of these cases were in metro Atlanta. Users, he said, tend be teenagers and those in their 20s.

Staff writer Helena Oliviero contributed to this article.