More than 100 people were arrested last night, most in Southeast Washington, as more than 200 D.C. police officers and other law enforcement personnel took part in a stepped-up installment of Operation Clean Sweep, the city's long-term antidrug operation.

Noting that all 200 officers assigned to Clean Sweep were involved in last night's operation, D.C. police officials said it was one of the largest crackdowns under the 15-month-old program, which has resulted in more than 26,000 arrests.

Police set up roadblocks and served at least one search warrant in far Southeast Washington where a dozen neighborhoods are known as drug markets and many homicides have been linked to drugs.

Last night's arrests were made on a variety of charges, including traffic violations, and it could not be immediately learned how many involved drugs.

Earlier this year, police said that drug-related charges had been placed against about 55 percent of the people picked up during Clean Sweep.

Five arrests were made last night on drug-related charges at an apartment house at 4234 4th St. SE, where a search warrant was served, police reported.

They said bags of what was believed to be crack, a cocaine-based drug, were tossed from the building, along with a .38-caliber handgun, when police arrived.

Arrest totals were mounting rapidly last night as the effort continued. At one roadblock, four arrests came within 10 minutes. Overall, officers said it was difficult to keep roadblocks in place because officers posted at them quickly became involved in processing arrested people.

The operation involved U.S. Park Police officers and members of the Naval Investigative Service and federal Bureau of Alcohol, Tobacco and Firearms.

Last night's operation appeared to be the first of its size in some time to be mounted as part of Clean Sweep, a program that includes undercover drug purchases and observation of street activity as well as roadblocks.

It also appeared to be the largest at least since an officer was shot Dec. 1 during an incident that stemmed from an undercover operation in far Northeast in the Mayfair Mansions-Paradise Manor area, another neighborhood that has been plagued by drugs, police said.

In one of the major previous crackdowns within Clean Sweep, police in late August arrested 72 persons and seized about $13,000 worth of what they described as illegal drugs in an 11-hour action on the streets around Mayfair Mansions and Paradise Manor.

Operation Clean Sweep was designed to clear drug dealers and purchasers from the streets, according to police officials who assert that a large proportion of crimes committed in the city are related to drugs.

The program, in which millions of dollars in drugs have been seized, has been particularly costly to operate because it requires huge amounts of overtime pay for the officers involved, who often take part in Clean Sweep in addition to their regular-duty shifts.

Costs in the first year of the program were estimated at $5.6 million.

The location of last night's operation in Southeast appeared to be at least partly a response to the upsurge in what police have described as drug-related shootings there.

Earlier this year, Assistant Police Chief Isaac Fulwood said drugs were involved in about 30 of the first 50 slayings recorded in the portion of Southeast Washington included in the 7th Police District.

Neighbors interviewed last night near one of the roadblocks expressed support for the police operation.

One woman who asked that her name not be used said she and her neighbors were happy that the police were working to remove drugs from the streets.

Staff writer Sari Horwitz contributed to this report.