BRIDGEPORT, Conn. (AP) _ The wail of ambulance sirens filled the air Thursday as construction workers marked a week since at least 23 colleagues died in an apartment building collapse and as searchers recovered three more bodies.

Twenty-eight construction workers were buried in tons of concrete and steel when the unfinished building gave way April 22. Six men remained missing Thursday, officials said.

Ambulances waiting outside the L'Ambiance Plaza site as the search went on sounded their sirens at 1:30 p.m., the time of the collapse.

Four bodies were pulled Thursday from the rubble, once piled about 40 feet high but now reduced to below ground level.

The search for the missing focused on areas near the building's exits.

''We're beginning to come to the conclusion that perhaps before the building fell, some people headed for the exits,'' said Jonathan Best, director of the rescue effort. ''... Maybe they had the opportunity to run.''

Officials still were hopeful of finding some survivors, although there were no indications of life, Best said.

Meanwhile, families of victims continued burying the dead, with one funeral held Thursday and others set for Friday and Saturday.

About a dozen residents of Pontelandolfo, Italy, ancestral home to eight of the dead, arrived Thursday night in Waterbury for a week's stay to console grieving relatives.

An estimated 12,000 residents of the Waterbury area are immigrants or descendants of immigrants from the Apennine town about 53 miles northeast of Naples.

''I cannot express in words what we feel inside our hearts,'' Pontelandolfo Mayor Carlo Guerrera said through a translator. ''Pontelandolfo has cried and is still crying for these victims.''

Guerrera, whose eyes welled with tears, thanked Angel Antonio Perugini for a cup of coffee that the victim had bought for him during Christmastime in Italy. He also remembered Michael Addonna, another victim, and Francisco Addonna, who is still missing, as close childhood friends.

Meanwhile, an expert on post-disaster trauma from the University of Maryland, Dr. Jeffrey Mitchell, met Thursday with emergency medical personnel who have been monitoring the stress and fatigue of rescue workers.

Some of the workers have grown hostile toward news reporters. At least one worker disconnected the power supply cord to a television reporter's live broadcast from the scene Wednesday night.

''As time goes on, people begin to lose hope,'' Best said. ''... We still believe there may be some people alive and it's hard to convince people of that after a certain period of time.''

Large steel beams bent toward the center of what would have been a 13-story building, indicating the path of the collapse and hinting that the building fell in on itself, fire Chief Paul McKenna said.

Investigators had no solid theory as to the cause, but engineers hired to review project records have said several factors may have played a role in the tragedy.

Reports have said investigators were the possibility that cement was improperly cured or that the ground beneath the structure was too weak to support it.

In addition, engineers inspecting city records have said the project lacked temporary bracing to prevent lateral movement in the steel columns while thousands of tons of concrete flooring were being jacked into place.

The $17.3 million building was being constructed by the lift-slab technique, in which concrete slabs are poured at the construction site and then raised into place by hydraulic lifters set into the support columns.

The city, insurance companies, the developer, the contractors and the Occupational Safety and Health Administration all have said they plan separate inquiries.