Share of Aecom Technology Corp. dropped 17 percent on Tuesday after the professional technical services company cut its full-year earnings guidance.

The Los Angeles company, which works on construction and other infrastructure projects for commercial and government clients, reported net income of $70.7 million (70 cents a share) for the quarter ended June 30, 11 percent higher than in the same period a year earlier. Revenue fell 22 percent to $2.07 billion.

Analysts surveyed by Thomson Reuters on average had expected the company to report profit of 64 cents a share on revenue of $2.10 billion.

In lowering its outlook, Aecom cited deterioration in its Australian mining business, and slower conversion of backlog in its Americas region. The company now expects full-year earnings of $2.30 to $2.40 a share, lower than the Wall Street consensus average of $2.45.

Even so, Chief Executive John M. Dionisio touted new business the company had won in the quarter.

“In a challenging growth environment, we booked $1.9 billion in new wins, which contributed to our $16.8 billion in backlog,” Dionisio said in a statement. “We also saw on-going strength in emerging markets, such as Asia, Africa and the Middle East.”

Shares closed down $5.84, or 17 percent, to $29.36 on the New York Stock Exchange.