SAN FRANCISCO (Bloomberg) — Bermuda-based Marvell Technology Group Ltd., a chipmaker that plans to restate financial results, said a probe by regulators into its stock-option grants has escalated.The review by the US Securities and Exchange Commission has become a formal investigation, Marvell, which is run from Santa Clara, California, said in a filing late on Tuesday. The company, which makes chips used in computing and communications systems, first received a letter of informal inquiry in July last year requesting certain documents.

In October, Marvell said it would restate results for more than six years to account for costs from misdated option grants. It's among more than 200 companies that have disclosed internal or federal probes into whether executives inflated the value of stock options by dating them to times when shares traded lower.