(Reuters) - Shares in British water firms United Utilities and Severn Trent fell after a water regulator on Tuesday opened enforcement cases into them, as well as two others, as part of its ongoing probe into wastewater management.

United Utilities and Severn Trent were among the top percentage losers on the blue-chip FTSE 100 index, falling about 1.5% and 1% respectively in early trading.

(Reporting by Aby Jose Koilparambil in Bengaluru; Editing by Nivedita Bhattacharjee)