Amazon says it is retraining its staff after “mistakenly” blocking Christian advertisements.

The retail giant is responding to questions from someone who has sold “Christian fashion gifts” on its platform for the past two years, but whose ad was recently blocked.

In an emailed response, Amazon said the content of the ad—which included images of Christian apparel with Biblical quotes—violated a new policy and added that others using similar language about religion would soon be taken down as well. “Products related to a specific religion are not allowed to be advertised,” wrote an Amazon representative. “The other sellers who are currently advertising religious-related products are doing incorrect practice, which may lead to their account suspension.”

But a spokesperson for Amazon told CNBC, “The email … contains inaccurate information and our long-standing policies have not changed. Corrective training is being provided to the relevant teams.”

A number of other sellers have recounted similar situations on Amazon Seller Forums. One was told that Amazon was “working to stop all advertising of religious items,” and was informed that crosses, Bibles and similar products could be restricted from advertising for promoting a “specific religion.”

For some sellers, the sudden suspension of ads has made a significant dent in their revenues. “Our revenue on Amazon is directly connected with advertising we do,” a seller told Faithwire.

According to Amazon’s ad policy page, the company prohibits content that advocates or demeans a religion. “Ads may contain references to a specific religion or faith in a historical or fictional context if the primary purpose is to entertain,” the policy states.

This is not the first time the online marketplace has come under fire for blocking conservative voices. Last year, The Daily Caller reported that Amazon had barred the faith-based legal advocacy group, Alliance Defending Freedom (ADF), from its Amazon Smile charity program. Peter Hasson of the Daily Caller News Foundation found that Amazon relies on groups like the Southern Poverty Law Center—which has had its own credibility crisis lately—to determine which groups are permitted to take part in its charity. According to Hasson, although ADF was excluded, a number of openly anti-Semitic organizations remain in Amazon’s charity network.