HOUSTON (Bloomberg) — Bermuda-based Nabors Industries Ltd., the world's largest onshore oil and natural-gas driller, said US securities regulators concluded a probe of backdated options grants to executives and don't plan to take enforcement action.US Securities and Exchange Commission staffers informed the company that they plan to close the informal inquiry, Nabors said yesterday in a filing with the commission. The company, based in Bermuda and run from Houston, in March said an internal review found incorrect dates were used in granting stock options to senior executives between 1991 and 1997.

The additional compensation expenses resulted in a pre-tax charge of $51.6 million against fourth-quarter 2006 earnings. Nabors is one of at least 200 companies to have disclosed internal or federal investigations into executive options that have so far resulted in earnings restatements, revisions and charges exceeding $9.6 billion.

The internal probe examined whether Nabors backdated grants to coincide with days when the stock price was low, giving recipients a greater profit, or failed to properly account for the awards.