Nabila Nanfuka, 22, of Neasden, north-west London, died in Lava Ignite in St Peter's Street in the early hours:
Eight other people were injured, with two in a critical condition in intensive care at Northampton General.
Supt Andy Cox said police would need help from witnesses to find out how many people had been in the club.
Northamptonshire Police has urged anyone who took mobile phone video footage or photographs to upload them via the force's website.
Supt Cox said officers had gone to the club shortly after midnight as part of a "pro-active patrol", more than three hours before the incident, and had been aware of large numbers at the 1,600-capacity venue.
"During the course of the evening it became apparent that there was a significant number of people at the nightclub but I must stress that it appeared to be an orderly event," he said.
"Were there too many people in there? We don't know."
Officers are also looking at claims a fire alarm prompted a rush for the exits.
Ms Nanfuka was studying leisure and tourism at the University of Northampton.
Superintendent Andy Cox says the event at the Lava Ignite club "appeared to be orderly"
Speaking outside the family home, Fahad Msimbe, 19, said his sister was his "best friend".
"She affected so many people's lives and put other people first," he added.
"She is one in a million really."
He said Miss Nanfuka had been to two similar events and "wanted to see if it would be as good as the previous ones".
"She just wanted to have a good time with her friends," he said.
The event, called DNA Presents Wickedest Wickedest, started at 21:00 BST on Tuesday and was due to go on until 04:00 BST on Wednesday.
Emergency services were called to the scene at 03:37.
One witness, James Adetula, 21, said a "stampede" had begun as people made for the exits when they were told that their buses were leaving.
Miss Nanfuka died soon after her arrival at hospital. Six people were treated for minor injuries and a number of people were treated at the scene, the hospital said.
A spokesman for Northampton Borough Council said it had been formally approached by police and on Thursday would hold a summary review to consider the premises licence for Lava Ignite.
A special sub-committee of the licensing panel will meet to consider evidence put forward by the police and decide what action to take.
A spokesman for Lava Ignite said: "The club management and staff are co-operating fully with the local police to find out exactly what happened.
Our thoughts are with the family of those involved.
Happend 19 OCTOBER 2011,