A new seating system that is set to be installed at London Stadium could cost up to £50m (€58.6m/$62.5m), pushing the total cost of converting the London 2012 Olympic stadium to more than £750m.
According to the Daily Mail newspaper, owners could pull out retractable seating and replace it with a hydraulic system, incurring further costs.
However, engineers estimated it could take up to three weeks to reconfigure the lower tier of the stadium, which could in turn have an impact on the number of events that the stadium could host.
London Stadium is the new home of English Premier League club West Ham United, and as the football season runs from July to late May, this offers only a two-month window to developers.
However, the facility is slated to host other events during the summer months, such as athletics meetings as part of contractual obligations, and this could mean further disruption to the plans.
The reports come after London Mayor Sadiq Khan ordered an investigation into the venue’s finances due to rises in costs.
In a statement a stadium spokesperson said: “The Mayor has recently announced an investigation into the seating at the stadium and we will await its conclusion before making a decision on the long-term plans for the seats.”