Officials at Chicago O’Hare’s international mail facility report an increase in shipments of synthetic drugs from China and Europe. Some of these drugs are extremely potent, according to the New York Daily News.

The drugs are being shipped in letters and packages, the article notes. Many of the drugs have been sold online. They include synthetic marijuana and methamphetamine, as well as a new type of Ecstasy. They arrive in bulk or in small packets that are sold for anywhere between $30 and $500 each.

Some of the synthetic drugs are 100 to 800 times more potent than the original versions, according to William Wagner of the Chicago Customs and Border Protection (CBP) Laboratory. “We are seeing a whole new level of synthetic highs coming to America,” he said in a news release. “Our CBP chemists have tested hundreds of samples and uncovered emerging trends in the increase in variations of synthetic marijuana, bath salts and other synthetic drugs.”

When a questionable substance is detected at a CBP facility, officers detain the shipment and send samples to chemists for analysis. If the shipment is found to contain an illegal substance, it is seized.

“These unpredictable chemical combinations are sending some users to the hospital and others to the grave,” said Steven Artino, CBP Chicago Acting Director of Field Operations.