The Justice Department has reportedly opened an insider trading investigation at Equifax

Equifax officials are reportedly being investigated by the Justice Department after selling stock before the company revealed a data breach that exposed the personal information of millions of Americans.

Bloomberg's Tom Schoenberg and Anders Melin reported that the US Justice Department is investigating whether top company officials violated insider trading laws when they sold Equifax shares before the company disclosed the hack.

According to Bloomberg, the department is looking at sales by Equifax Chief Financial Officer John Gamble, President of US Information Solutions Joseph Loughran, and President of Workforce Solutions Rodolfo Ploder.

Bloomberg cited "people familiar with the investigation" who asked not to be named because it is confidential.

Equifax last week reported a massive data breach, saying hackers may have accessed the personal details, including names and Social Security numbers, of more than 143 million consumers from mid-May to July. Equifax, which said it learned of the breach in late July, also said credit card numbers for about 209,000 people and certain documents for another 182,000 were also accessed.

The disclosure was swiftly met with criticism because of the delay in alerting the public to the hack, as well as problems with the website Equifax set up for people to check whether their details were at risk.

The three senior executives dumped almost $2 million worth of stock days after the company learned of the breach. An emailed statement from the credit-monitoring agency said the executives "had no knowledge" of the breach beforehand.

The sales were first reported by Bloomberg News' Anders Melin who said none of the sales appear to be part of pre-scheduled trading plans that allow executives to sell stock at regular intervals. All of the executives still owned thousands of shares of the company after the sales were completed, filings show.

Equifax's stock was little changed at 10:41 a.m. ET on Monday. Shares have tumbled by nearly 35% since the news of the hack broke.

Check out the full story at Bloomberg here.