Northern Rail is urging customers to check before they travel in the wake of the Manchester terrorist attack.
With the city's Victoria station likely to remain closed for the next few days while investigations continue, the firm is now operating an emergency timetable for services that would normally stop there.
As a result there is ongoing impact to many services, in particular those serving the Greater Manchester region.
Northern advises all customers to check before they travel by going to National Rail Enquiries or Northern Journey Planner.
Regional director Liam Sumpter said: "Manchester Victoria station will remain closed on Wednesday and it could be several days before it reopens.
"We are working to provide as many services as possible while the station remains closed, but customers need to be aware that there may be some short notice cancellations and delays.
"Our thoughts are with the families and friends of the people who have lost their lives and those who were injured on Monday evening."
More updates on train timetables and plans for reopening Manchester Victoria Station will be provided on Northern’s website, www.northernrailway.co.uk. For timetable information, please go to http://ojp.nationalrail.co.uk/service/planjourney/search or http://www.journeycheck.com/northern/.