S&P said: "We suspended our rating on ADY because of a lack of information we consider of sufficient quality from the company on its financial and operating performances and prospects. In particular, we are missing sufficient information on the company's operational volumes, tariffs, capital expenditures, and cost information for the first half of 2015, and on the details of its financial forecasts for the next two years (assumed tariffs, volumes, and investment projects).

"If the company provides us with sufficient information on its performances, we could reinstate the ratings. We also need further updates on ADY's current liquidity position. We will consider withdrawing the ratings if we do not receive the above-mentioned information within 90 days.

"Standard & Poor's may suspend a rating, in rare circumstances, if there is an expectation that the rating is likely to be reinstated. The suspension does not imply that ADY is not servicing its obligations. Should sufficiently detailed information become available, Standard & Poor's will reconsider an appropriate rating."