(Updates with closing index numbers and background on graft scandal)
BUENOS AIRES, Aug 7 (Reuters) - Argentine stocks plunged on Tuesday, with banks and energy companies leading losses, as investor concerns grew that a corruption probe that began with more than a dozen arrests last week could touch more companies.
Argentina's Merval stock index closed down 3.8 percent, marking the sharpest single-day fall since late June.
"Investors are very attentive to news coming out of the judicial investigation that has engulfed politicians and businessmen," local consultancy Portfolio Personal said in a note.
A wide-reaching investigation launched last week swept up construction magnates accused of attempting to secure contracts by delivering millions of dollars in bribes to officials in former president Cristina Fernandez's government.
Stocks for steel company Ternium fell on Tuesday by 6.1 percent, following a 5.8 percent tumble on Monday after Ternium's parent company Techint said it had been questioned by investigators and would continue cooperating after its offices were raided last week. (Reporting by Jorge Otaola and Walter Bianchi; Writing by Luc Cohen and Scott Squires; Editing by Sandra Maler Editing by Jonathan Oatis)