Detroit police stormed a Roman Catholic church in the community known as Poletown yesterday just before dawn and rounded up a dozen squatters, including a 71-year-old woman parishioner, who opposed the leveling of the neighborhood to make room for a Cadillac plant.

A dwindling corps of the community's Polish immigrant residents, aided by consumer activists from Washington, had for the past month staged a rag-tag resistance in the basement of the Immaculate Conception Church on Trombly Street, even after the city turned off the water and the Lights.

Their doomed struggle to save the church pitted the few remaining, mostly aged, devotees of a dying inner-city neighborhood against a determined city establishment operating under the banner of economic necessity.

The siege ended yesterday when police, denied entry by the squatters, hooked a tow truck to the basement door and ripped it off its hinges. As officers herded the group out, city workers moved in and removed crosses from walls and bells from the tower and dismantled pews. The demolition crews were right behind them.

"We're going to pray for your souls because you're going to need it," an elderly woman called out to the work crews as they hauled out pieces of the church organ. Others just watched from behind police barricades. Those inside the church had rung the bells to summon neighbors when the police arrived.

It seemed a classic confrontation of strong against weak, with the combined might of the City of Detroit, the Catholic archdiocese and General Motors Corp. arrayed against the likes of Josephine Jakubowski, 71, who invested most of her life in the spiritual and social activities of the parish. She was one of those inside the church when police arrived. At first, they tried to arrest only the men. But Jakubowski and several other women insisted on being officially charged too, according to the police.

Jakubowski cried at the police station, when she thought she might not be arrested, according to Detroit Free Press reporter Marianne Rzepka, 29, who had camped out at the church to watch the confrontation after one of the resisters alerted her. "For 35 years I worked. All those cakes that had to be baked, I baked them. You can't let me go now without arresting me," Jakubowski was quoted as saying.

All 12 of them arrested were later released when the prosecutor's office declined to pursue the charges.

A spokesman for the local Catholic archdiocese, which had sold the church to the city, issued a statement in support of the police action. Officials reportedly had considered closing the cavernous, ornate old structure anyway as its enrollment declined and the cost of heating the old church increased. General Motors earlier had offered to move the structure, but Cardinal John Dearden vetoed the idea.

The nation's Motor City, staggered by auto plant closings and other economic problems, desperately needs the 6,000 jobs which the new Cadillac plant will preserve. Most Poletown residents were pleased at the city's buy-out offer, made under a new "quick-take" act under the eminent domain doctrine, and the chance to move elsewhere, according to city officials.

A spokesman for Mayor Coleman Young, noting that Poletown's population was half black, also angrily denounced suggestions that "a black administration has been riding roughshod over white Polish immigrants at the behest of a behemoth industrial giant . . . Nobody wrote a line, much less waved a TV camera in anybody's face," when in years past entire neighborhoods of blacks were uprooted to make way for freeways.