An employee at the Queens district attorney’s office was accused on Thursday of threatening to detonate a device at a New York City migrant shelter after the police found explosive materials in his home, according to a complaint filed in Queens criminal court.

The employee, Derek Klever, told an unnamed witness last week that he was constructing an explosive device — by combining incendiary powders from fireworks with nail gun cartridges — to set off at a migrant shelter next to his apartment in Elmhurst, Queens, according to the complaint.

That person told the police that Mr. Klever said he was fed up with migrants “having a party at 8 in the morning” at the shelter, according to the complaint.

“This is a war,” Mr. Klever is said to have told the witness. “I wish I had a big enough one to blow them back to Venezuela.”

The police searched Mr. Klever’s home shortly after arresting him at his workplace on Tuesday. They found a BB gun in a child’s bedroom, as well as various fireworks, green wire and a vase filled with long nail cartridges and “a black substance,” both wrapped in tin foil, according to the complaint.

Mr. Klever was arraigned on Thursday and pleaded not guilty on charges of making a terroristic threat and criminal possession of a weapon, among other charges.