LOS ANGELES (AP) — Scientists have figured out all the steps to make morphine and similar painkillers without growing opium poppies, raising the possibility of home-brewed drugs.

While no one has yet reported making morphine in the laboratory from scratch, concerns are already being raised about potential abuse.

A team led by researchers at the University of California, Berkeley, genetically engineered yeast to mimic poppy plants, which are grown to provide opium from which morphine is derived. They discovered the last missing step in a long process to make morphine by hacking the DNA of yeast.

Findings were published Monday in Nature Chemical Biology.

It’s difficult for people to make morphine on their own because the process is still inefficient. But UC Berkeley researchers and others are calling for regulations and other restrictions.