Enbridge Inc’s ruptured pipeline, which leaked about 1,200 barrels of crude into a rural Wisconsin field 10 days ago, seemed like no big deal.

The scene was contained within hours, the line repaired within days. The leak was miles from running water or endangered wildlife. The immediate impact was limited to the evacuation of two houses and “veterinary attention” for some horses and cows.

And yet some experts and traders warn that Canada’s Enbridge might not be able to restart its 318,000-barrel-per-day Line 14 for weeks – or even months – as a once-obscure U.S. regulatory agency gets more comfortable with flexing its recently enhanced muscles.

The Pipeline and Hazardous Materials Safety Administration is in the spotlight after two big accidents in 2010 – BP Plc’s Macondo disaster in the Gulf of Mexico and another Enbridge leak of 20,000 barrels into Michigan’s Kalamazoo River in one of the biggest spills onshore.