Two Greenville County sheriff's deputies noticed a disturbance at Lavish Lounge just before 2am and saw a large crowd running out of the building, Sheriff Hobart Lewis said at a press conference.

There was "active gunfire from inside the building," Lieutenant Jimmy Bolt said in an initial statement, and Lewis said all the shots were fired inside.

Both Lewis and Bolt initially said 12 people had been wounded - with at least four in critical condition, Lewis said - but Bolt told the Associated Press that two victims were likely counted twice in the confusion at the hospital.

No one was immediately taken into custody.

Bolt told the AP that the sheriff's office was looking for two suspects but couldn't provide names or descriptions.

"We don't really have a person of interest that we can name," Lewis said at the press conference, later adding that authorities weren't sure what led to the gunfire.

Lewis said a "very large crowd" was at the nightclub for "some type of concert".

A post on Lavish Lounge's Facebook page advertised a July 4 performance by trap rapper Foogiano.

An Instagram direct message from the AP wasn't immediately returned but a bookings representative told the AP via text message that Foogiano was fine and his team was safe.

Under restrictions imposed in March to restrict the spread of the coronavirus in South Carolina, gatherings of 50 or more people in a single room are off-limits.

It was not immediately clear how many people were in the club at the time of the shooting.

Australian Associated Press