Rangers' Europa League clash against Bayer Leverkusen is set to be affected by measures to tackle coronavirus after state authorities in Germany issued a ban on major gatherings.
The North-Rhine Westphalia authority declared on Tuesday afternoon that events with more than 1,000 expected visitors should be cancelled or played behind closed doors.
The decree raises the prospect of Rangers fans being shut out of the second leg of the last-16 tie on March 19.
Rangers – who host the Bundesliga side this Thursday – have said their encounter is unaffected but the situation could change "quickly and dramatically".
North-Rhine Westphalia is the worst-affected region of Germany with more than 500 confirmed cases and the country's first two deaths.
The state government issued a decree that local authorities should "generally cancel events with more than 1,000 expected visitors".
A statement added: "Alternatively, you can, for example, check that there are no major audience events at major sporting events."
Health minister Karl-Josef Laumann said: "The virologists I spoke to recommend that we avoid large crowds wherever possible.
"We therefore have to think very carefully about what we can do without. I believe that school classes or public transport, for example, are essential. That would paralyse our social life.
"But we should initially cancel large trade fairs, congresses, concerts or sporting events."
Speaking about the second leg, a Rangers statement read: "The club is in continuous dialogue with Bayer Leverkusen and the authorities over this upcoming fixture.
"The current situation is that the match will proceed as planned with supporters attending the game but this could change quickly and dramatically in the coming days. Direction will have to be taken from the German authorities.
"We appreciate the uncertainty this situation will be causing for our travelling fan base and the club will endeavour to update supporters at every available opportunity."
Leverkusen said in a statement issued to the PA news agency: "There might be empty fan sections in the stadium due to the coronavirus.
"At this point, we can say that we are taking all the steps that the authorities consider useful and necessary."