The public are being warned to avoid V11 Tongwell Street where a mains sewage pipe has burst.
Anglian Water is managing the repair and clean-up operation at the Pineham site, run by The Parks Trust.
Due to the hazardous nature of the material, BMX track users and members of the public are advised to stay away.
While it is being cleaned up, the BMX track will be closed to the public.
A spokesman for The Parks Trust said: “At present, we have no timescales for the reopening of the BMC track.”
If you require further information, contact Anglian Water directly on 0800 771 881.