The operator of four of Maine’s eight medical marijuana dispensaries has voluntarily recalled two varieties of its cannabis after finding high levels of microbes during lab tests.

Wellness Connection of Maine says it is recalling a portion of a recent harvest of strains named “Blue Dream” and “LA Confidential” because of higher than acceptable levels of microbes, which are microorganisms – such as bacteria – that can sometimes cause diseases.

Becky DeKeuster, co-founder and director of education for WCM, said microbes are found in the air and most of what we eat. But she said that in high enough concentrations, they can become molds that pose a health risk.

DeKeuster said the microbes turned up in routine testing of two strains grown at the WCM. The level of microbes neared the company’s internal standards, she said – there are no state or federal standards. The company, she said, was concerned that mold could form if customers stored the marijuana in containers with too much humidity or heat, and that led to the recall.

“It was in a range that threw up a caution flag,” she said Saturday.

DeKeuster said the microbes are killed by high temperatures, so customers who smoked or cooked the marijuana would probably not ingest them. But the company was concerned that when customers handled the marijuana, they could be exposed to mold. That could cause respiratory problems, she said, particularly if the patients had asthma.

DeKeuster said about 500 of WCM’s 10,000 customers were affected by the recall.

“LA Confidential,” she said, is used as a pain reliever, for relaxation and for treating insomnia. “Blue Dream,” DeKeuster said, is usually used for digestive problems and to treat depression.

The company said no adverse effects have been reported in connection with the marijuana. Customers are being notified by mail and offered a refund, it said.

The company operates dispensaries in Portland, Brewer, Gardiner and Thomaston. DeKeuster said the recalled pot was one harvest of each of the two strains, grown at the company’s facility in Auburn.

The company said it tracks its medical marijuana from seed to sale as required by the state, and it has set up its own testing procedures and quality standards that include the use of a third-party laboratory, which it said exceeds state requirements and industry standards.

In 2013, the state fined Wellness Connection $18,000 for using pesticides on its cannabis in violation of state laws and rules. However, the company’s president said that it had stopped using the pesticides of concern and relied on natural pest controls.