State public health officials have approved the first 20 licenses to operate medical marijuana dispensaries, the first in Massachusetts under a voter-approved law.

The announcement was made Friday by the state Public Health Department, which had been reviewing applications from 100 finalists seeking to operate the dispensaries.

Licenses were awareded to Compassionate Care in Fairhaven and Medical Marijuana of Mass. in Taunton. No licenses were awarded in New Bedford.

The law allows marijuana to be used for certain medical conditions, including cancer, multiple sclerosis and Parkinson's disease.

The list covers 10 of the state's 14 counties, including two in Boston. The law perrmits up to 35 outlets in the state. It was not immediately clear when additional licenses would be granted.

The Massachusetts Medical Society, in a statement Friday, cautioned that the effectiveness of marijuana as a treatment has never been scientifically proven.

(Associated Press)