SAN JOSE (CBS SF) — Arson investigators with specially trained dogs resumed the search Thursday morning for possible human remains in the debris of a burned-down building near downtown San Jose.

The front area of a former television studio building burned to the ground in a fire reported at about 3 p.m. Sunday after a suspected arsonist sprayed flammable liquid on a mattress while homeless people living in the building were present inside, Santa Clara County prosecutors said.

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Human remains detection dogs appeared to detect at least one corpse in the debris on Wednesday and firefighters started to dig, but the debris was too heavy to lift, San Jose fire Capt. Cleo Doss said.

The search was temporarily halted at 6 p.m. and resumed Thursday morning.

One of the dogs, a female named Piper, sat down in the center of the collapsed former KNTV station at 645 Park Ave. at about 10 a.m. Thursday and firefighters placed a blue plastic cover on the ground and started to dig.

Piper has found hits in three separate locations but investigators “have not come up with anything,” Doss said.

The “hits” indicated by the dogs, which sit down when they pick up the scent of remains, is regarded as possible evidence that still has to be confirmed, Doss said.

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Two human remains detection dogs, Piper and a black-colored male named Kato, continued sniffing at the scene this morning.

Stillman Pfeffer, 55, was charged in Superior Court in San Jose on Wednesday with felony arson and burglary in connection with the fire and prosecutors said he may be charged with murder if human remains are found in the charred building.

Three people remain unaccounted for who were reportedly in the building, according to an arson unit report used by prosecutors to charge Pfeffer.

A witness to the alleged arson identified Pfeffer as the suspect following the fire and said her 4-month-old puppy perished in the blaze.

Doss confirmed this morning that investigators had found the remains of the puppy in the debris. Animal control officers placed the remains into a black bag and transported it away.

Doss said firefighters hope to conclude the investigation by Thursday.

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