Minutes after Sharmba Mitchell scored a fourth-round knockout Saturday night in Atlantic City, he was taken from the auditorium in police custody and spent the rest of his weekend in a New Jersey jail, the result of a warrant issued against him in Washington weeks ago, his lawyers said.

Mitchell, a 140-pounder from Takoma Park who earned more than $140,000 for his win, was released yesterday afternoon by a federal magistrate judge in Camden, N.J., on condition that he return to this area to resolve the matter, one of his lawyers said.

Details of the legal matter that led to the boxer's being jailed could not be immediately learned last night. Anthony Fusco Jr., a lawyer who represented him in New Jersey, said it was domestic rather than criminal.

Mitchell's handlers and the lawyer representing him in Washington said the boxer believed that whatever the issue, it had already been resolved.

Although his handlers expected the arrest -- they had been in contact with police authorities before the fight and had arranged to postpone it until after the bout -- Mitchell entered the ring unaware an arrest was pending.

Mitchell's camp decided to keep word of it from Mitchell to "keep his mind clear" for the fight. Mitchell looked sharp in the ring, improving to 51-3 with an impressive knockout of Carlos Vilches before 1,450 at Bally's Casino.

Police met Mitchell, 32, as he came down from the ring.

"Quite frankly, everything was very calm," said Jeff Fried, a Washington attorney and Mitchell's longtime legal adviser. "We were all trying collectively to ascertain what was going on.

"The New Jersey State Police were actually quite pleasant."

Police waited outside the locker room while Mitchell showered, then they led him to a police station in the casino. It was anything but a typical post-fight victory scene.

"Sharmba was obviously very disappointed," Fried said. "He would have preferred to celebrate a big victory with his family and friends and instead he was dealing with this and he was uncertain what it was all about."

Afterward, Mitchell continued to tell the police "there had been some kind of mistake," Fried said.

Fusco said Mitchell was held in the Atlantic County, N.J., jail on Sunday and part of yesterday until he was transferred to the custody of U.S. Marshals for the trip to Camden.

David Schertler, the lawyer retained to represent Mitchell in Washington, said he was confident that the matter can be cleared up as soon as the boxer gets back to Washington.