DENVER — City officials temporarily halted the sale of millions of dollars worth of legal marijuana because of concerns that unapproved pesticides or fungicides have contaminated it.

This past Friday alone, city officials placed a “hold” on 60,000 plants at a single grow facility here after consulting with state agriculture inspectors and the U.S. Environmental Protection Agency. They previously had placed crops from six other facilities on similar holds, allowing the plants to keep growing but blocking their sale to consumers.

Some growers have destroyed their crops instead of waiting for test results, which are still pending.

A mature marijuana plant can be worth more than $4,000 but it’s unclear where these plants were in the growing process. Because marijuana is such a lucrative crop, many growers improve their harvest by spraying young plants with chemicals that haven’t been approved for use on marijuana.