The shares lost 10.6 percent to $13.30 as investors decided to "sell first and ask questions later", according to analysts, who said that the delay to accommodate the company's audit committee could be interpreted as a warning sign.
The results will now be announced late next Tuesday, but the delay has raised speculation that Interpublic Group may have an "accounting problem".
"It's really hard to say what to make of this," Morgan Stanley analyst Michael Russell told the New York Times. "The postponement really could be thoroughness," he said. "We're in very careful times."
To make matters worse, corporate credit agency, Standard & Poor's has put the New York-based company's BBB+ long-term rating and its A-2 short-term rating on CreditWatch with negative implications.
The company's shares tumbled 24 percent on Monday after the company pushed back its second-quarter report to August 13, saying that its audit committee needed to "complete its review prior to management certification of its financial results".
Shares in Interpublic Group, owner of sports marketing company Octagon, continued to fall yesterday following the postponement of the advertising giant's second quarter results.
