Police want to speak to two men after an altercation “erupted” on a platform at the station, but say there is no evidence any weapons had been fired.
Officers also want to speak to anyone who was at the station about the cause of the mass panic and evacuation.
Sixteen people were treated after they were injured fleeing the station.
Oxford Circus was closed and armed police were deployed following reports that gunshots had been heard inside the station.
Police initially treated the incident as potentially terrorism-related, while nearby Bond Street station was closed amid fears of overcrowding.
The British Transport Police (BTP) said officers believe there was an altercation between two men on the platform before the scare.
They have released CCTV images of two men they want to speak to.
The Met said it began receiving “numerous” 999 calls reporting gunshots in Oxford Street and at Oxford Circus station at 16:38 GMT.
Oxford Circus – where Oxford Street and Regent Street meet – was cordoned off, while shops and businesses were placed in lockdown.
In a statement, the Met Police said: “Officers working with colleagues from British Transport Police carried out an urgent search of the area.
“No causalities, evidence of any shots fired or any suspects were located by police.” (Courtesy BBC)