American Tower (AMT) - Get Report fell 5% after the wireless-tower company joined the ranks of companies struggling with options and accounting questions.

The Boston-based company got a letter from the

Securities and Exchange Commission

requesting documents related to stock-option grants and practices.

American Tower said its board also created a special committee of independent directors to review past stock-option practices and related accounting. The special committee will be assisted by independent legal counsel and advisers, American Tower said.

The company said it initiated the review following the release of a third-party research report regarding practices related to the timing and pricing of stock-option grants. American Tower said it may need to correct its historical determinations of noncash stock-based compensation expense and possibly restate its financial statements.

The company intends to cooperate fully with the SEC.

The news comes as regulators probe stock option-granting practices at companies ranging from

Caremark

(CMX)

and

UnitedHealth

(UNH) - Get Report

to

Vitesse

(VTSS)

.

Early Friday, American Tower fell $1.61 to $30.