Prosecutor General Russian Ryaboshapka said his office will revisit 15 investigations, including ones involving the company, Burisma, and the owner of the company, former Ecology Minister Mykola Zlochevsky.
Hunter Biden served as a board member at Burisma from 2014 to 2019.
"Currently we are reviewing the criminal cases that have been previously pursued by the prosecutor general's office," Ryaboshapka said during a news conference. "The sphere you're talking about features Zlochevsky, [tycoon Serhiy] Kurchenko and other people and companies -- there are about 15 such cases."
He said the cases were "closed in violation of the law or other procedural violations."
Ryaboshapka told NBC News that the decision to review the cases was made after he took office in August, after a July phone call between President Donald Trump and Ukrainian President Volodymyr Zelensky in which Trump urged Ukraine to investigate Joe Biden.
The July phone call with Zelensky came under scrutiny last month after a whistle-blower in the intelligence community filed a complaint about it with the office of the director of national intelligence.
Trump and his personal lawyer, Rudy Giuliani, both said they have encouraged Ukraine to carry out an investigation into Joe Biden. Trump accused the former vice president of pressuring Ukraine to fire former Prosecutor General Viktor Shokin, who was investigating Burisma.
Shokin's successor, Prosecutor General Yuriy Lutsenko, told Bloomberg in May that the investigation into the company began before Hunter Biden joined the board, and he wasn't specifically a target of the probe. Additionally, Bloomberg reported the investigation into Burisma ended more than a year before Joe Biden called for the ouster of Shokin.
Multiple Western countries, including the United States, had called for Shokin's removal due to allegations of corruption.
Democrats said Trump's request of Ukraine amounts to asking a foreign country for help winning an election because Joe Biden is running to unseat Trump in the 2020 presidential election. House Speaker Nancy Pelosi launched an impeachment inquiry Sept. 24 after the White House released a memo detailing the July phone conversation.
Earlier Friday, the Democratic chairmen of three House committees released text messages showing Trump administration officials discussing Trump's dealings with Ukraine. Democratic lawmakers say the messages help clarify whether Trump threatened to withhold tens of millions of dollars in military aid to Ukraine unless Kiev agreed to investigate the Bidens.
In one text message, a senior American diplomat expressed outrage that the administration would withhold military aid until Ukraine complied with demands from Trump and Giuliani. The messages also revealed that top diplomat William Taylor threatened to resign last month amid concerns that Trump was withholding Ukrainian aid. Taylor has been the charge d'affaires at the U.S. Embassy in Kiev since June.
Taylor expressed concern that Trump would renege on the delivery of $400 million in military aid and strain relations between Washington and Kiev, to the benefit of Russia, which has occupied several border territories and the Crimea Peninsula since before fighting began in eastern Ukraine in 2014.
Nicholas Sakelaris contributed to this report.