By nightfall, police had cordoned off the block, and crime scene investigators and homicide detectives were moving in and out of the house.
They expected to be on the scene for several hours, Small said.
Police said one of the victims was 25. They did not release his name. The other men appeared to be in their 20s, but police did not know their names last night, Small said.
Police said they did not know why the men had been killed and had no suspects.
There were no signs of forced entry, Small said. Sections of the house appeared to have been ransacked, but police did not know what, if anything, had been taken. The house was not abandoned, he said, but he added that police did not know whether any of the men lived there.
Property records indicate that a 53-year-old woman owns the twin.
Officers took several witnesses to Police Headquarters to be interviewed by detectives.
Police recovered ballistic evidence that indicated that a semiautomatic gun had been used, Small said.
Small would not give extensive details of the scene so as not to "compromise the investigation."
The killings bring the city's homicide tally this year to 37, compared with 25 during the same period last year.
Inquirer staff writers Robert Moran and Mike Newall contributed to this article.