Transocean Ltd, the largest offshore drilling contractor, reported Wednesday a quarterly loss and an unexpected decline in revenue, sending its shares down 5 percent in after-hours trading.

The company posted a third-quarter net loss of $71 million, or 22 cents per share, compared with a profit of $368 million, or $1.15 per share, a year ago. Revenue fell 2 percent to $2.24 billion, below the average analyst estimate of $2.36 billion, according to Thomson Reuters I/B/E/S.

Operating and maintenance costs were $1.54 billion in the quarter, up 3 percent from the previous quarter, primarily due to maintenance, the company said in a statement.

Transocean shares were down 5.3 percent at $53.01 in after-hours trading following the release of the results.