handcuffs.JPGSan Francisco police this week announced hundreds of drug-related arrests stemming from a 21-day narcotics enforcement operation in the Mission District and Tenderloin neighborhood.

The operation, which ended Sunday, netted 212 arrests, police said. It involved narcotics teams and undercover officers from various district stations who purchased heroin, crack cocaine, methamphetamine and other illegal drugs.

Officers targeted the Mission and Tenderloin because of violence resulting from drugs sales on the street in those areas, police said.

Of the 212 people arrested, 31 percent were from out of town and 35 percent were on probation or parole, according to police.

The crackdown was the second major street-level operation by the Police Department in six months. A previous operation conducted in the Tenderloin in October 2009 netted 583 arrests, police said.

Despite the latest arrests, prosecutors have had to discharge many of the cases pending drug testing of the evidence by laboratories outside San Francisco.

Drug testing at San Francisco’s crime lab has been temporarily halted pending an investigation into alleged evidence tampering by a former crime lab employee.

Prosecutors have said they intend to re-arrest suspects and re-file cases once the outside tests are completed.

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