Up to 40,000 internet users across East Yorkshire have been left without broadband after a "major fault" affecting the Karoo service.
Engineers are working to resolve the problem which cut off the service for about half of Karoo's 75,000 broadband subscribers on Wednesday morning.
A spokeswoman for Kcom, Karoo's parent company, said it hoped to resume normal service "as soon as possible".
The firm has apologised for any inconvenience to customers.
Industry regulator Ofcom is currently carrying out a consultation into broadband services in Hull.
In a previous consultation it noted that several Hull residents had "expressed dissatisfaction that their choice of broadband supplier was limited, unlike the rest of the UK".