Thirty people were arrested Friday night in Northeast Washington at a marijuana pop-up event, authorities said.

Pounds of products containing marijuana and THC were taken from 28 vendors, a police lieutenant said on a police-community Internet bulletin board. THC is the principal psychoactive ingredient of cannabis, and marijuana is described as a form of cannabis.

According to the bulletin-board posting, police seized more than $10,000 in cash, and three firearms at the event in the 2200 block of 25th Place NE.

Any charges that were placed could not be learned immediately. Police said the arrests came in the course of serving a search warrant. According to the police official, the event was well-attended.

An earlier report in The Washington Post said such pop-up marijuana events have been thriving in the District. They have emerged in a kind of twilight zone of Washington marijuana law, under which small amounts of cannabis may be legally possessed but not legally sold.

However, some vendors said they did not think they had violated the law, saying that they were selling only trinkets and that any cannabis was included.

In an incident described in the Post account, 22 people were arrested and charged with misdemeanor drug possession with intent to distribute. But charges against the 22 were later dropped by D.C. prosecutors, according to the account. No reason was cited.

At the premises involved, according to the earlier Post account, those attending made “donations” that permitted them to receive what were described as gifts, which included edible or smokable items.

A lieutenant in the police narcotics unit has said the department does not actively seek out the markets but does respond to complaints.