Online supermarket Ocado has agreed a deal to set up a fourth major distribution centre, as it aims to satisfy increasing demand for online grocery shopping.On Thursday, the group said that it had clinched a deal to develop a new "customer fulfilment centre" in Erith, south east London.The project is set to be funded by Tritax Big Box REIT, with the fund saying it would provide £98.8m for the project, and developed by Bericote Properties.Ocado, whose third customer fulfilment centre is expected to open at the end of 2015, said that while planning consent was yet to be secured, it expected to begin work on the site in 2016 and begin operations in 2017.Ocado is yet to turn an annual profit since being founded in 2000 but analysts are estimating it will report a £10m profit and underlying core earnings of £71m for the year ended 30 November.Ocado shares were down 1.14% to 409.30p at 09:36 on Thursday.