Greece’s problems deepened on both sides of the Atlantic as the Federal Reserve disclosed it was investigating Goldman Sachs and other banks that helped the country mask its debts, and investors grew increasingly leery of lending any more money to a nation flirting with default.

Wall Street’s role in the run-up to the debt crisis has generated criticism and calls for an inquiry from European leaders. The Fed examination is the first time American regulators will examine the highly profitable if little-known business of supplying custom-made financial instruments to strapped countries on the Continent.

While Greece’s economic troubles have transfixed world markets for weeks, its problems have snowballed in recent days as workers went to the picket lines to protest budget cuts and the government struggled to raise cash to cover what is Europe’s largest budget deficit. Last year, Greece’s deficit equaled 12.7 percent of gross domestic product.

On Thursday, the Moody’s ratings agency joined Standard & Poor’s in warning that it might downgrade Greek government bonds, a move that would increase the premium Athens must pay to borrow. The move comes at a precarious time for Greece, which must raise 25 billion euros ($34 billion) over the next few months to avoid a sovereign default that officials fear could cause the finances of other weak European economies to collapse.