Photo by the Associated Press

(Philadelphia) -- Firefighters say one person has been killed in a building collapse in downtown Philadelphia.

Thirteen other people were injured in the accident.

The four-story building collapsed this morning. Several witnesses say they had been casting a wary eye on the demolition site and questioned how the workers were tackling the job.

Witnesses say they heard a loud rumbling sound immediately before the collapse.

The building once housed a first-floor sandwich shop and apartments above. Its collapse sent debris onto a Salvation Army corner thrift store next door.

The two properties are adjacent to an adult bookstore and theater that had been taken down earlier.