Verizon Communications Inc.’s top attorney said that the hack into Yahoo’s e-mail accounts represents a material impact to the phone carrier’s acquisition of the internet company’s online businesses. Verizon hasn’t definitively concluded that there was a material impact and is still waiting for Yahoo to complete its investigation into the situation, according to Bloomberg. Reuters reported earlier Thursday that Verizon General Counsel Craig Silliman saw reasonable basis for a material impact, which could let the company withdraw completely from the $4.83 billion deal.

Yahoo is confident in its value and continues "to work toward integration with Verizon," the company said.

The phone giant agreed in July to acquire the Yahoo core business. Verizon has planned to use the transaction to build upon its acquisition last year of AOL Inc., creating a digital advertising business that it hopes could rival Google and Facebook.

Last month. Yahoo announced that the personal information of at least 500 million users had been stolen in a 2014 cyberattack. The company has said the attack was carried out by a "state-sponsored" actor, but some private security experts have challenged that assertion.