The federal investigation into Hunter Biden and his tax affairs has reached a “critical stage,” a source told Fox News, as officials are looking into whether to charge President Biden’s son with various tax violations, possible foreign lobbying violations and more.

Hunter Biden has been under federal investigation since 2018, according to a source familiar with the matter.

A separate source told Fox News that the federal grand jury looking into Hunter’s business dealings wrapped up its latest term late last month, but said no charges have been filed.

The investigation is being conducted by Delaware U.S. Attorney David Weiss, a prosecutor appointed by former President Trump.

The source told Fox News Wednesday that Weiss and Justice Department officials were looking into whether to charge Hunter Biden with various tax violations and, more seriously, possible foreign lobbying violations. The source said Hunter Biden could face possible false statements charges.

But the source said no final decision has been made on whether to charge Hunter, and stressed that the investigation is ongoing.

Fox News first reported in December 2020 that Biden was a subject/target of the grand jury investigation, according to a well-placed government source. According to the source, a “target” means that there is a “high probability that person committed a crime,” while a “subject” is someone you “don’t know for sure” has committed a crime.”

The federal investigation into Hunter Biden was predicated, in part, by Suspicious Activity Reports (SARs) regarding suspicious foreign transactions.

Another source familiar with the investigation told Fox News in December 2020 that the SARs were regarding funds from “China and other foreign nations.”

A Treasury Department official, who did not comment on the investigation, spoke broadly about SARs, telling Fox News that SARs are filed by financial institutions “if there is something out of the ordinary about a particular transaction.”

The official told Fox News that the mere filing of a SAR does not mean there has been a criminal act, or violation of regulations, but instead, flags that a transaction is “out of the ordinary” for the customer. The official noted, though, that a SAR could be part of a money laundering or tax investigation.

Hunter Biden, weeks after the 2020 presidential election, released a statement acknowledging the federal investigation of his “tax affairs.”

“I take this matter very seriously, but I am confident that a professional and objective review of these matters will demonstrate that I handled my affairs legally and appropriately, including with the benefit of professional tax advisors,” Biden said in the December 2020 statement.

President Biden has repeatedly denied discussing Hunter’s business ventures with him.