MEMPHIS, Tenn. — A nightclub in Memphis, Tennessee is temporarily closing to review security operations after someone brought a gun into the business and shot four people Monday.

Police said shots rang out at about 3:25 a.m. during an altercation at Purple Haze Night Club, located just steps from historic Beale Street in downtown Memphis. One person was taken to a hospital in critical condition, and the other three were hospitalized in noncritical condition.

A fifth person suffered an undisclosed injury in the altercation at the club. One of those hurt was a security officer, the club said in a statement, but it was not immediately clear if the officer was shot.

No identities were released. No arrests have been made.

The after-hours club said in a statement that it has measures to detect guns as patrons enter the club and it is not sure how "those that discharged firearms were able to do so despite our strict security procedures."

"As the safety and security of our guests and employees are our utmost concern we are temporarily closing for two weeks to review operations," the nightclub's statement said.

A Memphis peace activist died after being shot outside of the club in April.