SAN FRANCISCO — Google shocked investors Thursday when it mistakenly filed its earnings report with the Securities and Exchange Commission several hours earlier than planned, reporting disappointing third-quarter profits.

Google stock dropped sharply after the report, down more than 9 percent, or $68 a share, before Nasdaq halted trading in its shares in the early afternoon. Shares resumed trading late in the day and were off 8.3 percent.

The mistaken filing surprised stock analysts, reporters and even Google’s own public relations staff, which did not know about it at first. Google later blamed the error on R.R. Donnelley & Sons, the publisher, which it said had filed an early draft of the earnings “without authorization.”

R.R. Donnelley, whose shares dipped as much as 5.6 percent before recovering, said in a statement that it had started an investigation to determine how the error happened.

Google said it would hold its conference call with Wall Street analysts as scheduled after the close of trading Thursday.

The company reported third-quarter revenue of $14.1 billion from both Google’s core search business and from Motorola Mobility, the ailing cellphone maker that Google recently acquired. This was an increase of 45 percent over the year-ago quarter. Net revenue, which excludes payments to the company’s advertising partners, was $11.33 billion, up from $7.51 billion.

But net income sank to $2.18 billion, or $6.53 a share, from $2.73 billion, or $8.33 a share. Analysts largely blamed losses from Motorola and a decline in Google ad prices for the poor results.

Later in the day, Google filed an amended earnings report with the SEC that included a statement from Larry Page, Google’s chief executive, calling it “a strong quarter.”

“At just fourteen years old, we cleared our first $14 billion revenue quarter,” Page said. “I am also really excited about the progress we’re making creating a beautifully simple, intuitive Google experience across all devices.” Even so, both net revenue and earnings were well below analysts’ expectations.

The miss was all the more surprising because Google shares had an outstanding quarter, increasing 35 percent over the past three months, in part because of strong performance in new businesses like display advertising as well as stumbles by competitors like Facebook. This month, Google’s market capitalization had edged ahead of Microsoft’s to make it second most valuable tech company, behind Apple, but it has again fallen behind Microsoft.