These three banks could lose $350 million if the Halliburton-Baker Hughes deal goes belly-up

Three banks could take a big hit if the Baker Hughes-Halliburton merger is called off by regulators in Washington D.C.

A Bloomberg report on Wednesday said the Halliburton deal could be stopped by regulators in Washington, D.C.

Both companies shares plummeted in the wake of the news.

Regulators are worried the deal will make the oilfield services industry too concentrated, Bloomberg reported, citing unidentified sources.

Baker Hughes stock fell by as much as 9%, stabilizing later at a loss of about 7%. Halliburton stock fell by about 4% before shares stabilized, at a loss of more than 2%. Halliburton said it remains committed to the deal, while Baker Hughes wasn't able to comment.

The deal was worth about $35 billion and with advisory fees in the 1% to 2% range for M&A, there could be around $350 million up for grabs for big banks if the merger goes through.

Credit Suisse served as lead advisor to Halliburton, joined by Bank of America Merrill Lynch.

But Goldman Sachs stands to lose even more if the deal collapses under regulatory pressure. Goldman was the lone advisor to Baker Hughes, which would have put it in line for a bigger check than Bank of America or Credit Suisse.

This isn't the first mega-deal in 2015 to be scotched at the finish line by regulators. Earlier this year, several boutique banks took a big hit when the Time Warner Cable-Comcast deal fell apart.