India's markets regulator has widened an investigation into alleged market manipulation by U.S. securities trading firm Jane Street to include other indexes and exchanges, a source familiar with the matter said.

Large buy or sell orders—executed seconds before close—nudge prices just enough to swing the outcome of options and futures contracts. It’s subtle. It’s fast.

The lawsuit alleged that the traders had stolen a “ highly valuable, unique, and proprietary ” trading strategy, which was quickly revealed to revolve around India’s booming options market. Jane Street and Millennium settled the lawsuit in December, but judging from SEBI’s report it has cast a long (and expensive) shadow.