At the Labor Department, they are pretty sure the Democrats did it. But they are not certain. And yesterday most Democrats said they were not too sure themselves how it happened.

But when White House and congressional negotiators finished work this week on a $500 billion, five-year budget package to cut the deficit, the Labor Department suddenly found itself with a potential new enforcement weapon against violators of federal health and safety laws.

Negotiators, in their search for revenue wherever they could find it, had plucked an old proposal for a five-fold increase in the size of the fines that could be imposed by the department's Occupational Safety and Health Administration (OSHA). In addition, the new budget agreement would authorize a tripling of fines by the department's Mine Safety and Health Administration.

Under the agreement, the maximum OSHA fines for non-serious violations would be increased from $1,000 to $5,000 per violation and fines for each serious violation would be raised from $10,000 to $50,000.

Maximum fines for mine safety violations would be increased from $10,000 to $30,000.

It was the only part of the budget where the negotiators decided to increase penalties to raise money. Projected revenues from the increased fines will rise from $95 million in the fiscal year just ended to more than $200 million a year over the next five years.

The five-year revenue projection is $1.1 billion.

The action was not lost on the business community. Mark D. Cowan, a former deputy assistant secretary of OSHA, denounced the action, calling use of fines as a way to increase budget revenues a "dangerous precedent."

Cowan called on the business community to "move quickly to address this proposal to protect the integrity of our occupational safety and health laws."

Cowan is chief executive officer of the Jefferson Group, which represents some of the corporations that have received the largest OSHA fines in recent years.

Earlier this year, the Labor Department had proposed a three-fold increase in safety penalties. A spokeswoman said yesterday that the department is endorsing the increase voted by the negotiators.

Although key officials in the Labor Department and at several congressional committees claimed ignorance when asked how the new fines found their way into the budget, sources at the Senate Labor and Human Resources Committee appeared to have the answer.

Several weeks ago, a committee source said, staff members for the budget negotiators came around to all congressional commitees and asked if there was anything that might be on the shelf that would bring in money.

"They were looking for money and they asked us what we had done lately," the source said. So the committee gave them the proposal to raise safety fines that had been dropped out of last year's budget reconciliation bill. The revenue estimates, the source said, were still fresh.