Canadian securities regulators have issued a warning to investors about claims being made by would-be medical marijuana companies, saying a review has concluded many are providing deficient information when announcing plans to join the sector.

Securities commissions in British Columbia, Alberta, Ontario and Quebec teamed up to review press releases issued by 62 publicly traded companies announcing plans to become marijuana producers under a new federal program that opened last April. The program will permit private-sector companies to grow and sell marijuana under license from Health Canada.

The regulators said 25 issuers “raised serious investor protection concerns” with announcements that were unbalanced and omitted key information, including their stage of development and the licensing process required by Health Canada. Most of them were at an early stage in their business development, with many having done virtually nothing to set up a marijuana business.

“In general, we found that issuers’ disclosures...