Police had sectioned off part of the Lancaster Canal and a road over it during Thursday in Preston.
Sidgreaves Lane, where it goes over the canal, was closed to traffic and pedestrians.
The footpath along the canal was closed from Lea Lane to Lea Road.
There was also no water traffic allowed along this stretch with all barges halted.
PC Stephen Connolly posted the warning and said: “If you’ll be doing the school run or commuting this morning please take note and plan an alternative route.”
The closure is following a barge fire near Darkinson Lane around 11pm on Wednesday (22 May).
Crews from Wesham and Penwortham attended the fire.
A spokeswoman for Preston Police said: “Officers and colleagues from the Fire Service attended and a joint investigation is underway into the cause of the fire.
“A section of the canal remains closed with no access between Lea Lane and Lea Road. Sidgreaves Lane is also currently blocked. This is whilst we carry our inquiries and so we apologise for any inconvenience this may cause for local residents.”
Anyone with information about the incident is asked to call police on 101 quoting incident reference 1654 of May 22.
Police reopened the canal bridge and footpaths shortly before 5pm.
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