LONG BEACH, Calif. (KABC) -- An investigation is underway after police say a man died under "possible suspicious circumstances" following a fire at a Long Beach fourplex.Long Beach Fire Department officials said the blaze broke out shortly before 11 p.m. Wednesday in the 500 block of W. 7th Street.Inside one of the units, firefighters found a man, who later died at a local trauma center. The man's identity was not released. He was said to be around 35 years old.Long Beach police described the death to have occurred under "possible suspicious circumstances" but did not elaborate.A young neighbor described the man as being kind, saying he always greeted her with a friendly hello.The blaze was contained to only one unit, with the damage confined mostly to an office area. The residents of the other three units were not displaced.Long Beach detectives were investigating the cause of the fire.