A cyclist drives past the Europa Building, also known as "The Egg" which was evacuated after toxic fumes from kitchen drains, forcing the European Union to switch the venue of its summit in Brussels less than 24 hours before leaders were due to begin the two-day meeting, in Brussels, Belgium, October 18, 2017. REUTERS/Yves Herman

BRUSSELS (Reuters) - The building that houses EU summits, where toxic fumes forced EU leaders to switch venues last week, will be closed for a further week as investigators seek to resolve the problem.

The fumes leaking from the drains have forced the Europa Building, also known as “The Egg”, to be evacuated twice this month, including before a summit of EU leaders on Thursday and Friday.

The new building was opened in January amid controversy over its 321-million-euro ($378 million) price tag.

Staff and meetings will be temporarily transferred to the next door Justus Lipsius building until the issue is resolved.

About 20 catering staff had to go to hospital on Oct. 13 and an unspecified number on Wednesday. An EU official said the Council and Belgian health and safety agencies believe the two incidents were due to the same source.