RIO DE JANEIRO — Rio police backed by helicopters and armored vehicles invaded a shantytown complex long held by traffickers on Sunday, quickly taking over the key drug gang stronghold, a top official said.Black-clad officers from elite police units entered the Alemao slum complex amid heavy fire, with TV images showing police and army helicopters flying low to support the men on the ground as hundreds of drug gang members tried to hold their position.But the officers encountered less resistance than expected and claimed victory, saying police were controlling the shantytown complex although many gang members still remained inside."We won," said Mario Sergio Duarte, head of Rio state's military police. "We brought freedom to the residents of Alemao."Officers on the ground, however, were saying they had not completely taken over the complex, and that gunmen were still fighting back. Gunfire could still be heard in the area."Without any doubt we know there are gang members hold up inside this slum still and we've got to go in and take them out," said one solider at the base of the slum who did not want to give his name because he was not authorized to speak to the media."Now it's time to be patient," Duarte said. "We've taken over the territory but it doesn't mean that we won't have confrontations with the gang members still inside. We have to be careful because they may be trying to set up traps for our men."At least five police helicopters were buzzing atop the Alemao, helping provide intelligence on where the gang members might be.Police and troops started moving up the slum inside armored vehicles as residents watched from their windows in shacks packed along steep hills. Massive tracked armored personnel carriers were moving in and out of the slum entrances on its southern edge, carrying soldiers with their faces painted.High-caliber rifle casings littered the streets for three blocks around the slum, and bloodied bandages were scattered on the ground near entrances where soldiers and police crouched behind buildings aiming their rifles toward the slum.Vehicles from the forestry service were seen moving around the shantytown complex, carrying soldiers to the jungle areas inside the slum to cut back trees and eliminate possible escape routes.There were no initial reports of police officers injured on Sunday.