HOUSTON -- A Houston-based company has been hired to investigate the cause of a stairwell collapse that killed two young boys and injured a third, officials said.

Mayor Bill White announced on Thursday that the Walter P. Moore firm, which specializes in forensic engineering, had been hired.  The company will review photos and records as part of the investigation of the July 16 collapse.

Killed by suffocating from debris that fell when the enclosed stairwell collapsed at the Westwood Fountains Apartments were David Vasquez, 10, and Miguel Angel Robledo, 4, whose deaths have been ruled accidental. The stairwell apparently was designed solely for maintenance workers to get to the roof.

“We’ve taken the death of these young people very seriously.  Our hearts go out to the families, and I’d ask apartment owners to think carefully about the integrity of their buildings,” White said in Friday’s online edition of the Houston Chronicle.

Officials said inspectors, in the future, may be asked to pay special attention to stairs during their visits.

“I wouldn’t doubt that, if somebody walked by it in the past before this tragedy, that an inspector would make a judgment by rattling the stairwell that all was fine,” said Andy Icken, a deputy director in the city’s Department of Public Works and Engineering.

The collapse is prompting some immediate changes. Officials said an apartment inspection coordinator and more staff will be hired at a $1 million a year price tag, to shore up the number of occupancy inspectors, currently at 10. They inspect Houston’s more than 2,500 multifamily properties.

Meanwhile, a lawsuit has been filed by the family of David Vasquez, against RVB Apartments Inc., which owns the apartment complex. The lawsuit alleges that apartment managers did not maintain safe conditions and did not warn residents about the unsafe conditions.

Attorney J. Michael Moore, representing the Vasquez family, said he plans to have the scene examined by experts. He said there had been numerous tenant complaints about the stairwell. The newspaper said a resident indicated the stairwell was often left unlocked.