BUFFALO, N.Y. (AP) _ Public officials accused of corruption frequently hide behind a stone wall of silence, but here they've built barricades to keep reporters out.

It's not every day, though, that a city parks commissioner is accused of deliberately polluting a lake.

Buffalo's Parks Department scandal has grown in two months from a relatively ordinary tale of accusations of kickbacks and purchasing irregularities to encompass the mayor's broken lawnmower and melted ice in a favorite skating lake.

In the process, it is threatening to bring the government of New York's second-largest city to a halt.

City council members want to talk to Parks Commissioner Robert E. Delano about the allegations and also about the ordinary business of government.

But he's stonewalling them.

Delano and Mayor James D. Griffin could not be located for comment Thursday. Delano has had no comment since the affair began. Griffin's only response has been to lavishly praise Delano, his longtime friend and handball partner, and to label complaining parks workers ''stool pigeons.''

''If the parks commissioner can't talk in public to the Common Council, it'll become almost impossible for us to manage the affairs of the city,'' Majority Leader Eugene Fahey said. ''... We have to prepare a city budget.'' But the prosecutor investigating the scandals said his entire probe could fall apart if the council subpoenas Delano because the parks boss could win immunity from prosecution if he is compelled to talk to the council.

''Unfortunately, city government finds itself at an impasse,'' U.S. Attorney Dennis C. Vacco wrote in a letter to Fahey.

''I respectfully suggest that the public interest in a thorough and orderly investigation into possible wrongdoing within the Parks Department would at this time outweigh the public's interest in the Common Council's efforts to perform its lawful role in the conduct of city government.''

The scandal began with allegations in November about private work done by parks workers on city time, various forms of favoritism and kickbacks, and purchasing irregularities.

It exploded last week, when news reports quoted unidentified parks workers as saying they had been ordered to pour brine into Delaware Park Lake to keep it from freezing after the Common Council took a lakeside refreshment stand concession away from Delano's associates. Brine is a saturated salt solution.

The melted ice struck a nerve because the lake, the centerpiece of the Frederick Law Olmsted park that officials call ''Buffalo's jewel,'' had just been cleaned of pollution at a cost of $12 million.

''Here's the guy who's supposed to protect our lakes, and he's giving orders to his men to pollute it,'' said Councilman Alfred T. Coppola, whose district includes the park. ''That's what's crazy about the whole thing.''

When the council asked Delano for an explanation on Tuesday, he refused to appear.

On the same day, the 3 1/2 -foot-high wooden barricade went up at the entrance to Delano's office suite. One worker told The Associated Press that the barricade was erected because toxic chemicals were stored in the building, but another told a television reporter that it was ''to keep you guys out.''

Griffin was linked to the scandal for the first time on Thursday by unidentified parks workers who told The Buffalo News that they had repaired the mayor's lawnmower and boat engine on city time, in a city shop, using city materials.

More tips of alleged wrongdoing are coming in every day, Coppola said. He showed reporters an anonymous letter he had received urging him to ''Check the fence purchases against their work orders.''

''Each day gets worse. Not only the city's image is at stake, we've got a whole department in turmoil,'' Coppola said.