The Rand Corp. has retracted a widely reported study that linked last year’s closing of hundreds of medical marijuana dispensaries in Los Angeles to a rise in crime rates in surrounding neighborhoods.

The Santa Monica, California-based think tank says in a statement Monday that questions raised after the study’s publication prompted an unusual internal review.

The review discovered that data described as covering the city of Los Angeles and surrounding areas did not include crime data reported by the Los Angeles Police Department.

Rand Vice President Debra Knopman terms it a “rare failure” of its peer-review system.

The study, published in September, was called “Regulating Marijuana Dispensaries: An Overview with Preliminary Evidence of Their Impact on Crime.”

Rand researchers plan to conduct a new analysis when they have adequate data.