SPRING VALLEY, N.Y. - The first hint that something was amiss came in the middle of the night when the neighbor called to report a smell of smoke. Police investigated and found the blaze, but it wasn't your typical fire.

It was an old school bus that had been converted into a supersized oven for Passover matzos _ complete with a smokestack, exhaust fans and working fire. A building inspector said that while the bakery bus wasn't nearly up to code, it was "very creative."

The derelict red-and-white bus, connected by a plywood passageway to a single-family house, was out of sight of casual passers-by in a Hasidic Jewish neighborhood and had apparently long escaped the notice of authorities. Its owner, Rabbi Aaron Winternitz, said Monday he had been making the unleavened bread there for three Passovers and was eager to do the same this year, with Passover coming up in a week.

He said that the oven-in-a-bus was his invention, and that he purposely bought an old school bus because "school buses are made strong and safe." He said the bus he purchased had also been used as a home and as a race-car carrier.

But a police spokesman in Spring Valley, a New York City suburb, described the setup as "a tinderbox." And Manny Carmona, Spring Valley's deputy building inspector, told Winternitz on Monday that he has to move the bakery bus away at least 10 feet from the house, disconnect the unauthorized gas line that was fueling the oven and come up with documents to show that a licensed engineer had overseen the project.

"It's too close. If something happens, it could spread to the house," Carmona said.

He acknowledged, after Winternitz took him inside, that the bus oven was "not as hazardous as it looks."

"The fire is contained properly," he said. "It looks safe, but you can't go on looks." He said he would hold off on any summonses to see if Winternitz could meet his obligations and would work with him to see if baking, perhaps with wood fueling the flames, could continue.

Police Sgt. Lou Scorziello said police traced the smoke to the bus at about 3 a.m. Friday. The oven, he said, "was up and running."

Given the illegal gas line, "There certainly was the potential for an explosion."

He said the back door of the bus, formerly the emergency exit, was the oven door.

"All the seats had been removed and the whole inside was an oven," he said.

Winternitz, who said he lived with his wife and three children in the light pink two-story house that fronted the bus, brushed aside any safety concerns.

"Everything was always done properly," he said. The rabbi said he made about 100 pounds of crispy matzo, in 10-inch square crackers, each Passover for his 50-member Congregation Mivtzar Hatorah. Observant Jews eat matzo during Passover week to illustrate how the Jews had no time to let their bread rise as they fled slavery in Egypt.

They also sometimes get rid of their leavened bread by burning it in ceremonial fires just before Passover, and in New York City, with its large Jewish population, the Fire Department issues a reminder to units every year about the ritual. Two years ago, the Fire Department said a fire that killed three Orthodox Jewish boys occurred because a gas stove burner was left on for three days, possibly to conform with a strict religious custom that forbids such activities as turning on lights or stoves during holy days.

Winternitz said that if he can't make his matzo this season, his congregation will have to eat store-bought matzo. Although he found the regulatory attention unwelcome, the rabbi said he understood why reporters were interested.

"It's something new that you never saw," he said. "Inventions are exciting. People are curious."