(Reuters) - Alberta's energy regulator on Tuesday ordered Syncrude Canada to develop a wildlife mitigation plan and publish more information following the death of 30 blue herons at an oil sands site in the Canadian province.

The Alberta Energy Regulator said on Saturday it had opened an investigation into the bird deaths at Syncrude Canada's Mildred Lake site, which is about 40 km (25 miles) north of Fort McMurray.

The regulator said on Tuesday the investigation is still under way, but issued the environmental protection order nonetheless. It ordered Syncrude to collect water and soil samples, develop and publish daily public reports and submit a final report to the regulator.

Syncrude said over the weekend it had already begun investigating and was cooperating with authorities.

In 2010, Syncrude was fined C$3 million ($2.29 million) for negligence in the 2008 deaths of 1,600 ducks in a toxic tailings pond, a case that fueled international concern about the environmental impact of developing Canada's oil sands.

Syncrude said it found the blue herons last week in a sump, or dugout, near a pump house, rather than a tailings pond.

Syncrude's partners include Canadian Oil Sands Ltd, Imperial Oil Ltd, Suncor Energy Inc, Sinopec, CNOOC Ltd's Nexen, Japan's Mocal Energy and Murphy Oil Co.

In November, the Alberta regulator cleared several oil sands operators of responsibility for the deaths of 196 waterfowl that landed on their toxic tailings ponds, saying poor weather forced the birds down.

(Reporting by Jeffrey Hodgson, editing by G Crosse)