Fairfax County police arrested about 20 people and seized drugs and gambling paraphernalia in two simultaneous raids Friday night.

The raids capped a five-month undercover investigation launched in response to local residents who complained about drug traffic and gambling in the area, police said. About 11 p.m., more than 40 uniformed and plain-clothes police swept into a crowded residence at 8015 Seaton St. in Gum Springs. Police said it housed an illegal gambling operation involving dice and card games.

About 15 people in the house at the time of the raid were charged with misdemeanor gambling violations. Two residents of the house, Thurman Bush, 67, and Thurman Bush Jr., were arrested on felony gambling charges. The elder Bush also was charged with illegal sale of alcoholic beverages. His son was charged with four counts of distributing marijuana, police said.

Fairfax police spokesman Warren Carmichael said drugs and drug paraphernalia also were confiscated in a raid on an apartment in the 7900 block of Richmond Highway. The house was empty at the time of the raid.

Those arrested were charged with more than 50 felony counts in connection with the investigation and others are still at large, Carmichael said.

Among those arrested were: Donald F. Bellfield, 41, of 3608 Buckman Rd. on charges of distribution of cocaine and marijuana, and Albert Triplett, 31, of 3649 Mariposa Pl. on charges of distribution of marijuana.