The U.S. Drug Enforcement Administration (DEA) has allowed the growing and distribution of marijuana for the purposes of research.

The DEA announced yesterday that it will permit other organizations to apply as registered marijuana suppliers to enable research groups, including universities, to conduct more clinical studies on the drug, RT News reports.

The policy change was made following a letter signed by eight senators, calling on the DEA to support more research about the medical benefits of marijuana.

"One thing I hear loud and clear from everybody, even the most conservative lawmakers, is that we need more research," David Caserett, researcher at the University of Pennsylvania, said in a report by New Scientist about the call for expanded marijuana research.

The University of Mississippi is currently the only agency-registered cannabis supplier for research. The 12-acre cannabis farm grows the plant for the National Institute of Drug Abuse's (NIDA) Drug Supply Program.

In the U.S., there are only 350 researchers who are registered to conduct cannabis research. But in 2015, only eight received cannabis shipments from the University of Mississippi's farm. This results in major backlogs and delays for the research groups' studies.

However, the DEA has decided not to change marijuana's Schedule 1 classification, which lists the drug alongside heroin, indicating that marijuana has a "high potential for abuse." The agency likewise denied two petitions to reschedule the drug under the Controlled Substances Act.

"Marijuana has no currently accepted medical use in treatment in the United States," Chuck Rosenberg, acting DEA administrator, wrote in the denial letter.

"Marijuana lacks accepted safety for use under medical supervision. At present, there are no [FDA-approved] marijuana products, nor is marijuana under a New Drug Application at the FDA for any indication."

In the U.S., 25 states have legalized smoking marijuana to treat certain medical conditions like glaucoma, nerve pain, and even cancer. However, marijuana use is still considered an offense under Federal law.