STAMFORD, Conn. (AP) — Police officers investigating what appeared to be a routine blight and code violation case walked into a potentially dangerous situation at a city home, finding explosive substances, shotguns, an underground tunnel and what appeared to be white supremacist and anti-police materials, authorities said Friday.

Local health officials were concerned the owner of the Vine Road home was illegally renting out rooms and took officers with them to execute a search warrant at the house Wednesday. But the search was called off when officers found potential bomb-making materials. Police obtained their own search warrant and sent the bomb squad in, Capt. Brian McElligott said.

Officers found unidentified powders and liquids that apparently could be used in explosives, a plastic pipe containing nuts and bolts that looked like a bomb and three shotguns legally registered to the homeowner.

In the basement, they discovered an uncompleted tunnel that ran under the backyard for a short distance but had no exit, McElligott said. There also was suspected white supremacist propaganda in the house, and hateful words were found written on a photograph of a police funeral, other police officials said.

Authorities said the house was filthy and smelled of dog urine and feces, and they removed two German shepherds from the home.

Officers searched and removed items from the house from Wednesday into Thursday morning. Police say the property is now safe and poses no threat to neighbors.

Police did not identify the homeowner, who hasn't been charged with any crime and has cooperated with police. McElligott said the powders and liquids are being tested and charges could be filed based on what the substances are.

McElligott said it's not clear why the homeowner was building a tunnel or whether he had plans to do harm.