At a news conference Wednesday, D.C. police said they seized $2.3 million worth of synthetic drugs from a warehouse in Northwest Washington. (Peter Hermann/The Washington Post)

D.C. police this week confiscated at least $2.3 million worth of synthetic drugs that were stored in a warehouse in Northwest Washington and destined for sale throughout the District, according to law enforcement officials and court documents.

“This is a massive and unprecedented seizure,” said Assistant Police Chief Peter Newsham, standing next to tables piled high with evidence bags filled with 19,247 small packets of strawberry-flavored drugs branded “Bizarro.” The total weight of the drugs was 265 pounds, police said.

Newsham said the operation, which included the Drug Enforcement Administration, Homeland Security and the Maryland State Police, showed the results of focusing “on the sources of these type of substances that are reeking havoc in our community.”

Police arrested Siraj Issa, 33, of Northwest Washington, and ­Yenework Abera, 41, of Alexandria, and charged each in federal court in the District with possession with intent to distribute synthetic cannabinoids. A U.S. District Court judge ordered them held until a hearing Tuesday.

Joseph Roll Conte, an attorney for Issa, declined to discuss details of the case but said his client plans to plead not guilty. Abera’s attorney could not be immediately reached for comment.

District police say they have carried out the largest seizure of synthetic drugs in the city's history on Tuesday, totaling a street value of more than $2 million. (WUSA9)

Authorities think most synthetic drugs on the market are manufactured in China. Authorities said they traced the shipment seized Tuesday from the West Coast to a shipping company in Howard County, between Washington and Baltimore, and then to the storage facility in Northwest.

Synthetic drugs have been around for years, but officials said the problem in the District spiked in June when paramedics recorded 439 ambulance trips for overdoses — about 15 per day, eight times the number from the corresponding time last year. Police have also attributed violence to the drugs, which can make users lethargic but also can make them agitated.

Although commonly called synthetic marijuana, officials say the drugs encompass a range of mind-altering substances, and that manufacturers continually alter the chemical formulas to avoid being labeled illegal drugs. The synthetic drugs are commonly sold on the street or in stores, packaged in multicolored packets adorned with pictures of cartoon characters.

Police said some users mix the synthetic drugs with PCP, and packets sell between $20 and $40, sometimes less than marijuana. Because of the overdoses, the District has given police expanded authority to shut down stores that sell the drugs, and targeting distributors has been a priority.

Authorities did not detail how they were tipped to the case. But an affidavit filed in U.S. District Court said police discovered the drug shipment during an investigation in Howard County on Aug. 27, and realized it was headed to the District. Authorities said they saw a large wooden pallet with boxes wrapped in plastic at the Howard site. A police dog became alerted to drugs, authorities said, and an undercover officer took a portion and had it tested.

While testing for synthetic cannabinoids can be difficult and elusive, police said this shipment contained chemicals already listed as banned by federal authorities. Undercover officers drove the shipment from Maryland to the District, and they said they met the men at the warehouse when they appeared together in a car. Police said the men were arrested after they unloaded the boxes onto a hand cart and locked them in a storage bin.

Previous seizures of synthetic drugs in the District were of no more than 1,000 to 2,000 packets, made in 2013 and 2014. Newsham said the two men arrested “were playing a major role in the distribution.”