By Dave Warner

PHILADELPHIA (Reuters) - The rescue of four starving, mentally handicapped people held captive in the filthy basement of a Philadelphia building began with a landlord's suspicions about a pair of dog bowls.

Turgut Gozleveli, a retired electrical contractor who cares for the building, told Reuters on Thursday how on a routine inspection a week ago, he noticed missing lightbulbs in the basement and dog bowls under a workbench table.

His discoveries ultimately led to the arrest of four people on kidnapping charges and the rescue of three men and a woman from the cramped basement dungeon in the working class Tacony neighborhood.

Authorities said the captors held the mentally handicapped adults to steal their Social Security checks, and investigators were pursuing the possibility as many as 50 people were victimized in a fraud scheme across several states.

Gozleveli, 71, who speaks with a Turkish accent, said he assumed a tenant had stolen the bulbs but was mystified by the bowls in the no-pets-allowed apartment building.

"I knocked on the doors and said, 'Is anyone feeding a pet?'" he recalled. All of the tenants he spoke to in the seven-unit building, once a small neighborhood movie theater, said no.

On Friday, he looked again and the bowls were still there.

On Saturday, he ventured down a few steps leading to a subbasement housing water heaters and another smaller room holding an out-of-use furnace.

Flashlight in hand, he saw a chain wrapped around the handle of the metal door to the old furnace room. He unwrapped the chain and opened the door to find two small barking dogs and piles of blankets on wooden platforms on the dirt floor.

He pulled back the edge of a dirty quilt to find a man and a woman huddled underneath. There seemed to be little else in the room except a urine-filled bucket that served as a toilet.

"I said, 'Get the hell out of here,'" he said, before calling police. "I thought they were squatters."

Inside the small room, police found two more men -- one in a ragged sleeping bag and one chained to the rusty furnace.

When they emerged into the daylight, "they were kind of beat up, walking like they were drunk, unsteady," the landlord recalled. Police said the victims were mentally challenged with the intellectual capacities of 10-year-olds.

Further search turned up yet another dog, a larger one penned inside a wooden enclosure that Gozleveli knew tenant Jean McIntosh used for storage.

McIntosh, 32, has been charged in the case, as has her mother, Linda Ann Weston, 51, who is suspected of being ringleader of the scheme. Weston has already served prison time for starving a man to death in her North Philadelphia apartment some 30 years ago.

Also under arrest are Gregory Thomas, 47, of North Philadelphia, and Eddie Wright, 50, said to be homeless.

"One of the people said 'Linda brought us here,'" Gozleveli said, an apparent reference to Weston.

Within a short time of his discovery, Gozleveli said the apartment building was swarming with dozens of police officers.

Gozleveli believed he found the victims in the nick of time, and said he was thankful he had not waited another day to start poking around the dark basement.

"They would have been dead," he said.

Once discovered, the victims were taken to area hospitals and placed in custodial care, officials said.

(Editing by Ellen Wulfhorst and Cynthia Johnston)